diff --git a/.eslintignore b/.eslintignore
index ba7d7e0..8f74907 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -2,3 +2,4 @@
 .vscode
 .github
 /node_modules
+/src/tests
diff --git a/src/environment.js b/src/environment.js
index 96a0ed1..e690480 100644
--- a/src/environment.js
+++ b/src/environment.js
@@ -7,7 +7,7 @@ class Environment {
     }
 
     setJeki (scope, name, value) {
-        if (this.vars[scope] == undefined) {
+        if (!this.vars[scope]) {
             this.vars[scope] = {};
         }
 
@@ -15,11 +15,11 @@ class Environment {
     }
 
     getJeki (scope, name) {
-        if (this.vars[scope] != undefined) { return this.vars[scope][name]; }
+        if (this.vars[scope]) { return this.vars[scope][name]; }
     }
 
     setIse (scope, iseName, iseNode) {
-        if (this.iseDeclarations[scope] == undefined) {
+        if (!this.iseDeclarations[scope]) {
             this.iseDeclarations[scope] = {};
         }
 
@@ -27,13 +27,13 @@ class Environment {
     }
 
     getIse (scope, iseName) {
-        if (this.iseDeclarations[scope] != undefined) {
+        if (this.iseDeclarations[scope]) {
             return this.iseDeclarations[scope][iseName];
         }
     }
 
     isExistHelperIse (iseName) {
-        return helperIseDeclarations[iseName] != undefined;
+        return helperIseDeclarations[iseName] !== undefined;
     }
 
     runHelperIse (iseName, iseArgs) {
diff --git a/src/helperise/array_helpers/ka.js b/src/helperise/array_helpers/ka.js
index d967b3b..8e52904 100644
--- a/src/helperise/array_helpers/ka.js
+++ b/src/helperise/array_helpers/ka.js
@@ -1,7 +1,7 @@
 // Get array length
 function ka (args) {
     if (args instanceof Array) {
-        const [param, ] = args;
+        const [ param, ] = args;
         if (param instanceof Array) return param.length;
 
         throw new Error("Invalid param given to helper ise ka.");
diff --git a/src/helperise/input_output/tesibi.js b/src/helperise/input_output/tesibi.js
index 5f6d668..e5a9040 100644
--- a/src/helperise/input_output/tesibi.js
+++ b/src/helperise/input_output/tesibi.js
@@ -3,7 +3,7 @@ const readlineSync = require("readline-sync");
 // Takes command line input
 function teSibi (args) {
     if (args instanceof Array) {
-        const [param, ] = args;
+        const [ param, ] = args;
         if (typeof param === "string") {
             const input = readlineSync.question(param);
             return parseFloat(input) || input;
diff --git a/src/helperise/string_helpers/si_leta_kekere.js b/src/helperise/string_helpers/si_leta_kekere.js
index 6ff2acf..3f877ec 100644
--- a/src/helperise/string_helpers/si_leta_kekere.js
+++ b/src/helperise/string_helpers/si_leta_kekere.js
@@ -1,7 +1,7 @@
 // Convert String to lower case
 function siLetaKekere (args) {
     if (args instanceof Array) {
-        const [param, ] = args;
+        const [ param, ] = args;
         if (typeof param === "string") return param.toLowerCase();
 
         throw new Error("Invalid param given to helper ise síLẹ́tàkékeré.");
diff --git a/src/helperise/string_helpers/si_leta_nla.js b/src/helperise/string_helpers/si_leta_nla.js
index 020ec05..6ad8f4c 100644
--- a/src/helperise/string_helpers/si_leta_nla.js
+++ b/src/helperise/string_helpers/si_leta_nla.js
@@ -1,7 +1,7 @@
 // Convert String to upper case
 function siLetaNla (args) {
     if (args instanceof Array) {
-        const [param, ] = args;
+        const [ param, ] = args;
         if (typeof param === "string") return param.toUpperCase();
 
         throw new Error("Invalid param given to helper ise síLẹ́tàŃlá.");
diff --git a/src/inputstream.js b/src/inputstream.js
index 431eb0f..dcd9e92 100644
--- a/src/inputstream.js
+++ b/src/inputstream.js
@@ -41,11 +41,11 @@ class InputStream {
     }
 
     isEndOfFile () {
-        return this.peek() == "";
+        return this.peek() === "";
     }
 
     isNotEndOfFile () {
-        return this.peek() != "";
+        return this.peek() !== "";
     }
 }
 
diff --git a/src/interpreters/helpers/woke_helper.js b/src/interpreters/helpers/woke_helper.js
index 5af8ede..b4aa791 100644
--- a/src/interpreters/helpers/woke_helper.js
+++ b/src/interpreters/helpers/woke_helper.js
@@ -3,7 +3,7 @@ const constants = require("../../constants.js");
 class WokeHelper {
     static isWokeVariable (context, tiName) {
         const wokeList = context.environment().getJeki(context.getCurrentScope(), constants.KW.WOKE);
-        return wokeList != undefined && wokeList.indexOf(tiName) != -1;
+        return wokeList && wokeList.indexOf(tiName) !== -1;
     }
 }
 
diff --git a/src/interpreters/ibase.js b/src/interpreters/ibase.js
index 2ce5ee3..310d049 100644
--- a/src/interpreters/ibase.js
+++ b/src/interpreters/ibase.js
@@ -1,6 +1,6 @@
 class IBase {
     constructor () {
-        if (this.constructor == IBase) {
+        if (this.constructor === IBase) {
             throw new Error("Cannot instantiate abstract class IBase");
         }
     }
diff --git a/src/interpreters/inodearrayelem.js b/src/interpreters/inodearrayelem.js
index 8ebab93..8ec7f97 100644
--- a/src/interpreters/inodearrayelem.js
+++ b/src/interpreters/inodearrayelem.js
@@ -23,7 +23,7 @@ class INodeArrayElement extends IBase {
             }
         });
 
-        if (arrayElement == undefined) context.throwError(`Index given for array ${node.name} does not exist`);
+        if (!arrayElement) context.throwError(`Index given for array ${node.name} does not exist`);
 
         return arrayElement;
     }
diff --git a/src/interpreters/inodecallise.js b/src/interpreters/inodecallise.js
index 7bc4ff4..1959c11 100644
--- a/src/interpreters/inodecallise.js
+++ b/src/interpreters/inodecallise.js
@@ -1,5 +1,4 @@
 const IBase = require("./ibase.js");
-const constants = require("../constants.js");
 
 class INodeCallIse extends IBase {
     interpreteNode (node) {
@@ -21,7 +20,7 @@ class INodeCallIse extends IBase {
 
     static getIseNode (context, iseName) {
         for (let index = context.scopeStack().length - 1; index >= 0; index--) {
-            if (context.environment().getIse(context.scopeStack()[index], iseName) != undefined) {
+            if (context.environment().getIse(context.scopeStack()[index], iseName) !== undefined) {
                 return context.environment().getIse(context.scopeStack()[index], iseName);
             }
         }
@@ -45,7 +44,7 @@ class INodeCallIse extends IBase {
     static runIseNodeBody (context, iseNodeBody) {
         for (let i = 0; i < iseNodeBody.length; i++) {
             const returnedValue = context.evaluateNode(iseNodeBody[i]);
-            if (returnedValue != undefined) return returnedValue;
+            if (returnedValue !== undefined) return returnedValue;
         }
     }
 }
diff --git a/src/interpreters/inodefun.js b/src/interpreters/inodefun.js
index ff68660..794ef53 100644
--- a/src/interpreters/inodefun.js
+++ b/src/interpreters/inodefun.js
@@ -9,7 +9,7 @@ class INodeFun extends IBase {
             for (let i = 0; i < node.body.length; i++) {
                 const returnedValue = this.evaluateNode(node.body[i]);
                 if (returnedValue === constants.KW.KURO) return;
-                if (returnedValue != undefined) return returnedValue;
+                if (returnedValue !== undefined) return returnedValue;
             }
 
             this.evaluateNode(node.increment);
diff --git a/src/interpreters/inodegetjeki.js b/src/interpreters/inodegetjeki.js
index 6660f3c..c3fa523 100644
--- a/src/interpreters/inodegetjeki.js
+++ b/src/interpreters/inodegetjeki.js
@@ -4,7 +4,7 @@ const WokeHelper = require("./helpers/woke_helper.js");
 class INodeGetJeki extends IBase {
     interpreteNode (node) {
         for (let index = INodeGetJeki.getTopIndex(this, node.name); index >= 0; index--) {
-            if (this.environment().getJeki(this.scopeStack()[index], node.name) != undefined) {
+            if (this.environment().getJeki(this.scopeStack()[index], node.name) !== undefined) {
                 return this.environment().getJeki(this.scopeStack()[index], node.name);
             }
         }
diff --git a/src/interpreters/inodeise.js b/src/interpreters/inodeise.js
index 1e0ad90..349634e 100644
--- a/src/interpreters/inodeise.js
+++ b/src/interpreters/inodeise.js
@@ -2,7 +2,7 @@ const IBase = require("./ibase.js");
 
 class INodeIse extends IBase {
     interpreteNode (node) {
-        if (this.environment().getIse(this.getCurrentScope(), node.name) != undefined) { this.throwError(`Ise with name ${node.name} already exists within the ${this.getCurrentScope()} scope`); }
+        if (this.environment().getIse(this.getCurrentScope(), node.name) !== undefined) { this.throwError(`Ise with name ${node.name} already exists within the ${this.getCurrentScope()} scope`); }
 
         this.environment().setIse(this.getCurrentScope(), node.name, node);
     }
diff --git a/src/interpreters/inodejeki.js b/src/interpreters/inodejeki.js
index bcc4089..3c976a7 100644
--- a/src/interpreters/inodejeki.js
+++ b/src/interpreters/inodejeki.js
@@ -21,7 +21,7 @@ class INodeJeki extends IBase {
         const topIndex = context.scopeStack().length - 2;
 
         for (let index = topIndex; index >= 0; index--) {
-            if (context.environment().getJeki(context.scopeStack()[index], node.left) != undefined) {
+            if (context.environment().getJeki(context.scopeStack()[index], node.left) !== undefined) {
                 return context.environment().setJeki(context.scopeStack()[index], node.left, INodeJeki.getValue(context, node.right));
             }
         }
@@ -33,7 +33,7 @@ class INodeJeki extends IBase {
         for (let i = 0; i < node.left.indexNodes.length; i++) {
             const arrayIndex = context.evaluateNode(node.left.indexNodes[i]);
 
-            if (arrayIndex === "" && i == node.left.indexNodes.length - 1) {
+            if (arrayIndex === "" && i === node.left.indexNodes.length - 1) {
                 // push right node to the last location in the array when index is empty
                 arrayLiteral.push(context.evaluateNode(node.right));
                 return;
@@ -64,7 +64,7 @@ class INodeJeki extends IBase {
 
     static getValue (context, node) {
         const value = context.evaluateNode(node);
-        if (value == undefined) context.throwError(`Cannot set value undefined to variable ${node.left}`);
+        if (value === undefined) context.throwError(`Cannot set value undefined to variable ${node.left}`);
         return value;
     }
 }
diff --git a/src/interpreters/inodenigbati.js b/src/interpreters/inodenigbati.js
index ac04b9f..881958f 100644
--- a/src/interpreters/inodenigbati.js
+++ b/src/interpreters/inodenigbati.js
@@ -7,7 +7,7 @@ class INodeNigbati extends IBase {
             for (let i = 0; i < node.body.length; i++) {
                 const returnedValue = this.evaluateNode(node.body[i]);
                 if (returnedValue === constants.KW.KURO) return;
-                if (returnedValue != undefined) return returnedValue;
+                if (returnedValue !== undefined) return returnedValue;
             }
         }
     }
diff --git a/src/interpreters/inodese.js b/src/interpreters/inodese.js
index 921afdd..1a94bbb 100644
--- a/src/interpreters/inodese.js
+++ b/src/interpreters/inodese.js
@@ -5,7 +5,7 @@ class INodeSe extends IBase {
     interpreteNode (node) {
         if (this.evaluateNode(node.condition) !== constants.KW.IRO) {
             return INodeSe.runBody(this, node.then);
-        } else if (node.else != undefined) {
+        } else if (node.else !== undefined) {
             return INodeSe.runBody(this, node.else);
         }
     }
@@ -16,7 +16,7 @@ class INodeSe extends IBase {
 
         for (let i = 0; i < body.length; i++) {
             const returnedValue = context.evaluateNode(body[i]);
-            if (returnedValue != undefined) return returnedValue; // it's an ise pada value or kuro statement
+            if (returnedValue !== undefined) return returnedValue; // it's an ise pada value or kuro statement
         }
     }
 }
diff --git a/src/interpreters/inodewoke.js b/src/interpreters/inodewoke.js
index d7c8354..182901d 100644
--- a/src/interpreters/inodewoke.js
+++ b/src/interpreters/inodewoke.js
@@ -5,7 +5,7 @@ class INodeWoke extends IBase {
     interpreteNode (node) {
         let woke = this.environment().getJeki(this.getCurrentScope(), constants.KW.WOKE);
 
-        if (woke == undefined) woke = node.varNames;
+        if (!woke) woke = node.varNames;
         else woke.push(...node.varNames);
 
         this.environment().setJeki(this.getCurrentScope(), constants.KW.WOKE, woke);
diff --git a/src/interpreters/inodeyi.js b/src/interpreters/inodeyi.js
index 98d8406..6783118 100644
--- a/src/interpreters/inodeyi.js
+++ b/src/interpreters/inodeyi.js
@@ -27,7 +27,7 @@ class INodeYi extends IBase {
     }
 
     static canRunPadasi (IRUIndex, node) {
-        return (IRUIndex === node.yibody.length - 1) && (node.padasi != undefined);
+        return (IRUIndex === node.yibody.length - 1) && (node.padasi !== undefined);
     }
 
     static runPadasi (context, padasi) {
diff --git a/src/interpreters/maininterpreter.js b/src/interpreters/maininterpreter.js
index 26692dd..db823e7 100644
--- a/src/interpreters/maininterpreter.js
+++ b/src/interpreters/maininterpreter.js
@@ -10,9 +10,9 @@ class MainInterpreter {
     }
 
     initScopeStack () {
-        const _scopeStack = ["global", ];
+        const _scopeStack = [ "global", ];
         this.getCurrentScope = () => _scopeStack[_scopeStack.length - 1];
-        this.scopeStack = () => [..._scopeStack, ];
+        this.scopeStack = () => [ ..._scopeStack, ];
         this.pushToScopeStack = (scope) => _scopeStack.push(scope);
         this.popFromScopeStack = () => _scopeStack.pop();
     }
diff --git a/src/lexer.js b/src/lexer.js
index b5b3231..522f609 100644
--- a/src/lexer.js
+++ b/src/lexer.js
@@ -44,10 +44,10 @@ class Lexer {
         const stringEnd = constants.SYM.STR_QUOTE;
         this.inputStream.next(); // needed to skip the opening quote symbol '"'
         const str = this.readWhile((ch) => {
-            return ch != stringEnd;
+            return ch !== stringEnd;
         });
 
-        if (this.inputStream.peek() == stringEnd) { this.inputStream.next(); } // needed to skip the closing quote symbol '"'
+        if (this.inputStream.peek() === stringEnd) this.inputStream.next();// needed to skip the closing quote symbol '"'
         else { this.throwError(`Expecting '${stringEnd}' but found unexpected char`); }
 
         return { type: constants.STRING, value: str, };
@@ -69,7 +69,7 @@ class Lexer {
     readNumber () {
         let hasDot = false;
         const num = this.readWhile((ch) => {
-            if (ch == constants.SYM.PERIOD) {
+            if (ch === constants.SYM.PERIOD) {
                 if (hasDot) return false;
                 hasDot = true;
                 return true;
@@ -82,7 +82,7 @@ class Lexer {
 
     skipComments () {
         this.readWhile((ch) => {
-            return ch != constants.SYM.NEW_LINE;
+            return ch !== constants.SYM.NEW_LINE;
         });
         this.inputStream.next(); // skips the "\n" symbol
     }
@@ -92,11 +92,11 @@ class Lexer {
         if (this.inputStream.isEndOfFile()) return null;
 
         const ch = this.inputStream.peek();
-        if (ch == constants.SYM.COMMENT) {
+        if (ch === constants.SYM.COMMENT) {
             this.skipComments();
             return this.readNext();
         }
-        if (ch == constants.SYM.STR_QUOTE) return this.readString();
+        if (ch === constants.SYM.STR_QUOTE) return this.readString();
         if (this.isDigit(ch)) return this.readNumber();
         if (this.isIdentifier(ch)) return this.readIdentifier();
         if (this.isPunctuation(ch)) return { type: constants.PUNCTUATION, value: this.inputStream.next(), };
diff --git a/src/parsers/basenode.js b/src/parsers/basenode.js
index ba1fb93..88a56b6 100644
--- a/src/parsers/basenode.js
+++ b/src/parsers/basenode.js
@@ -1,7 +1,7 @@
 class BaseNode {
     // Make BaseNode act like an interface.
     constructor () {
-        if (this.constructor == BaseNode) {
+        if (this.constructor === BaseNode) {
             throw new Error("Cannot instantiate abstract class BaseNode");
         }
     }
diff --git a/src/parsers/keywordnodes/kwnodefun.js b/src/parsers/keywordnodes/kwnodefun.js
index bf4bfa9..1ec7a36 100644
--- a/src/parsers/keywordnodes/kwnodefun.js
+++ b/src/parsers/keywordnodes/kwnodefun.js
@@ -40,11 +40,11 @@ class KwNodeFun extends BaseNode {
     static isInValidFunIncrementStatement (funNode) {
         const incrementNode = funNode.increment.right;
 
-        if ([constants.SYM.PLUS, constants.SYM.MINUS, ].indexOf(incrementNode.operation) >= 0) {
+        if ([ constants.SYM.PLUS, constants.SYM.MINUS, ].indexOf(incrementNode.operation) >= 0) {
             // e.g fun (tí i =0; i < 10; tí i = i + 1;)
             // make sure there is variable 'i' in atleast one child of the incrementNode
             // i.e jeki i = i + 1 or jeki i = 1 + i or jeki i = i + i
-            if ([incrementNode.left.name, incrementNode.right.name, ].indexOf(funNode.init.left) >= 0) {
+            if ([ incrementNode.left.name, incrementNode.right.name, ].indexOf(funNode.init.left) >= 0) {
                 return false;
             }
         }
diff --git a/src/parsers/keywordnodes/kwnodegbewole.js b/src/parsers/keywordnodes/kwnodegbewole.js
index 09b114f..52b93f2 100644
--- a/src/parsers/keywordnodes/kwnodegbewole.js
+++ b/src/parsers/keywordnodes/kwnodegbewole.js
@@ -9,9 +9,9 @@ class KwNodeGbeWole extends BaseNode {
         const node = {};
         node.operation = constants.KW.GBE_WOLE;
 
-        if (this.lexer().peek().type == constants.STRING) {
+        if (this.lexer().peek().type === constants.STRING) {
             node.path = leafnl.getNode.call(this);
-            if (path.extname(node.path.value) != constants.YL_EXT) { this.throwError("Invalid yorlang file. Expected file with .yl extension"); }
+            if (path.extname(node.path.value) !== constants.YL_EXT) { this.throwError("Invalid yorlang file. Expected file with .yl extension"); }
 
             this.skipPunctuation(constants.SYM.STATEMENT_TERMINATOR);
             return node;
diff --git a/src/parsers/keywordnodes/kwnodeise.js b/src/parsers/keywordnodes/kwnodeise.js
index aaaf665..bb2e379 100644
--- a/src/parsers/keywordnodes/kwnodeise.js
+++ b/src/parsers/keywordnodes/kwnodeise.js
@@ -11,7 +11,7 @@ class KwNodeIse extends BaseNode {
     }
 
     static isExpectedIseDeclaration (context) {
-        return context.getBlockTypeStack().length == 0 || context.peekBlockTypeStack() === constants.PROGRAM ||
+        return context.getBlockTypeStack().length === 0 || context.peekBlockTypeStack() === constants.PROGRAM ||
                                                     context.peekBlockTypeStack() === constants.KW.ISE;
     }
 
diff --git a/src/parsers/keywordnodes/kwnodeyi.js b/src/parsers/keywordnodes/kwnodeyi.js
index 61991fe..47fdf6d 100644
--- a/src/parsers/keywordnodes/kwnodeyi.js
+++ b/src/parsers/keywordnodes/kwnodeyi.js
@@ -36,7 +36,7 @@ class KwNodeYi extends BaseNode {
     }
 
     static isNextTokenIru (context) {
-        return context.isNotEndOfFile() && context.lexer().peek().value == constants.KW.IRU;
+        return context.isNotEndOfFile() && context.lexer().peek().value === constants.KW.IRU;
     }
 
     static getPadasi (context) {
diff --git a/src/parsers/nodeLiterals/arraynl.js b/src/parsers/nodeLiterals/arraynl.js
index b3cc6d6..614f4a7 100644
--- a/src/parsers/nodeLiterals/arraynl.js
+++ b/src/parsers/nodeLiterals/arraynl.js
@@ -3,7 +3,7 @@ const constants = require("../../constants.js");
 
 class ArrayNl extends BaseNode {
     getNode (arrayNameToken) {
-        return (arrayNameToken == undefined) ? ArrayNl.getParsedArrayLiteral(this)
+        return (!arrayNameToken) ? ArrayNl.getParsedArrayLiteral(this)
             : ArrayNl.getParsedArrayElement(this, arrayNameToken);
     }
 
@@ -28,7 +28,7 @@ class ArrayNl extends BaseNode {
     }
 
     static getArrayElementIndexNodes (context) {
-        const indexNodes = [ArrayNl.getArrayElementIndexNode(context), ];
+        const indexNodes = [ ArrayNl.getArrayElementIndexNode(context), ];
 
         while (context.isNextTokenPunctuation(constants.SYM.L_SQ_BRACKET)) { // handles multi-dimensional array element
             indexNodes.push(ArrayNl.getArrayElementIndexNode(context));
@@ -48,7 +48,7 @@ class ArrayNl extends BaseNode {
     }
 
     static isNotEmptyArrayIndex (context) {
-        return context.lexer().peek().value != constants.SYM.R_SQ_BRACKET;
+        return context.lexer().peek().value !== constants.SYM.R_SQ_BRACKET;
     }
 }
 
diff --git a/src/parsers/nodeLiterals/callIseNl.js b/src/parsers/nodeLiterals/callIseNl.js
index d2d674b..e6d900a 100644
--- a/src/parsers/nodeLiterals/callIseNl.js
+++ b/src/parsers/nodeLiterals/callIseNl.js
@@ -20,7 +20,7 @@ class CallIseNl extends BaseNode {
             this.parseExpression.bind(this), null
         );
 
-        if (iseNameToken.value == undefined) this.skipPunctuation(constants.SYM.STATEMENT_TERMINATOR);
+        if (iseNameToken.value === undefined) this.skipPunctuation(constants.SYM.STATEMENT_TERMINATOR);
 
         return node;
     }
diff --git a/src/parsers/nodeLiterals/keywordnl.js b/src/parsers/nodeLiterals/keywordnl.js
index 40d4389..853c578 100644
--- a/src/parsers/nodeLiterals/keywordnl.js
+++ b/src/parsers/nodeLiterals/keywordnl.js
@@ -15,11 +15,11 @@ class KeywordNl extends BaseNode {
             return leafNl.getNode.call(this);
         }
 
-        this.throwError(`Expecting yorlang keyword value e.g boolean(iró|òótó) but found ${token.value}`);
+        this.throwError("Expecting yorlang keyword value e.g boolean(iró|òótó)");
     }
 
     static isKeywordNl (context) {
-        return [constants.KW.OOTO, constants.KW.IRO, ].indexOf(context.lexer().peek().value) >= 0;
+        return [ constants.KW.OOTO, constants.KW.IRO, ].indexOf(context.lexer().peek().value) >= 0;
     }
 }
 
diff --git a/src/parsers/nodeLiterals/variablenl.js b/src/parsers/nodeLiterals/variablenl.js
index e177398..cfced64 100644
--- a/src/parsers/nodeLiterals/variablenl.js
+++ b/src/parsers/nodeLiterals/variablenl.js
@@ -7,7 +7,7 @@ class VariableNl extends BaseNode {
         const varNameToken = this.lexer().next();
 
         const nextTokenValue = this.lexer().peek().value;
-        if (variableNlTypes[nextTokenValue] != undefined) {
+        if (variableNlTypes[nextTokenValue]) {
             const variableNlType = variableNlTypes[nextTokenValue];
             if (variableNlType instanceof BaseNode) return variableNlType.getNode.call(this, varNameToken);
             else throw new Error(`Dependency ${variableNlType} must be of type BaseNode`);
diff --git a/src/parsers/parser.js b/src/parsers/parser.js
index 96fe406..5e87d04 100644
--- a/src/parsers/parser.js
+++ b/src/parsers/parser.js
@@ -18,7 +18,7 @@ class Parser {
         };
         this.popBlockTypeStack = () => _blockTypeStack.pop();
         this.peekBlockTypeStack = () => _blockTypeStack[_blockTypeStack.length - 1];
-        this.getBlockTypeStack = () => [..._blockTypeStack, ];
+        this.getBlockTypeStack = () => [ ..._blockTypeStack, ];
     }
 
     initIsArithmeticExpression () {
@@ -31,17 +31,17 @@ class Parser {
 
     isNextTokenPunctuation (punc) {
         const token = this.lexer().peek();
-        return token && token.type == constants.PUNCTUATION && (token.value == punc);
+        return token && token.type === constants.PUNCTUATION && (token.value === punc);
     }
 
     isNextTokenOperator (op) {
         const token = this.lexer().peek();
-        return token && token.type == constants.OPERATOR && (token.value == op);
+        return token && token.type === constants.OPERATOR && (token.value === op);
     }
 
     isNextTokenKeyword (kw) {
         const token = this.lexer().peek();
-        return token && token.type == constants.KEYWORD && (token.value == kw);
+        return token && token.type === constants.KEYWORD && (token.value === kw);
     }
 
     skipPunctuation (punc) {
@@ -70,15 +70,15 @@ class Parser {
     }
 
     parseAssign () {
-        return this.parseWhile([constants.SYM.ASSIGN, ], this.parseOr);
+        return this.parseWhile([ constants.SYM.ASSIGN, ], this.parseOr);
     }
 
     parseOr () {
-        return this.parseWhile([constants.SYM.OR, ], this.parseAnd);
+        return this.parseWhile([ constants.SYM.OR, ], this.parseAnd);
     }
 
     parseAnd () {
-        return this.parseWhile([constants.SYM.AND, ], this.parseGreaterLesserEquality);
+        return this.parseWhile([ constants.SYM.AND, ], this.parseGreaterLesserEquality);
     }
 
     parseGreaterLesserEquality () {
@@ -92,11 +92,11 @@ class Parser {
     }
 
     parsePlusMinus () {
-        return this.parseWhile([constants.SYM.PLUS, constants.SYM.MINUS, ], this.parseMultiplyDivisionRemainder);
+        return this.parseWhile([ constants.SYM.PLUS, constants.SYM.MINUS, ], this.parseMultiplyDivisionRemainder);
     }
 
     parseMultiplyDivisionRemainder () {
-        return this.parseWhile([constants.SYM.MULTIPLY, constants.SYM.DIVIDE, constants.SYM.REMAINDER, ], this.parseNodeLiteral);
+        return this.parseWhile([ constants.SYM.MULTIPLY, constants.SYM.DIVIDE, constants.SYM.REMAINDER, ], this.parseNodeLiteral);
     }
 
     parseWhile (operatorList, parseOperationWithLesserPrecedence) {
@@ -121,14 +121,14 @@ class Parser {
     parseNodeLiteral () {
         const token = this.lexer().peek();
 
-        if (nodeLiterals[token.type] != undefined) {
+        if (nodeLiterals[token.type]) {
             const nodeliteral = nodeLiterals[token.type];
             if (nodeliteral instanceof BaseNode) return nodeliteral.getNode.call(this);
             else throw new Error(`${token.value} must be of type BaseNode`);
         }
 
         // check if the token value is a punctuation that can be used in an expression e.g (, [
-        if (nodeLiterals[constants.EXP_PUNC][token.value] != undefined) {
+        if (nodeLiterals[constants.EXP_PUNC][token.value]) {
             const nodeliteral = nodeLiterals[constants.EXP_PUNC][token.value];
             if (nodeliteral instanceof BaseNode) return nodeliteral.getNode.call(this);
             else throw new Error(`${token.value} must be of type BaseNode`);
@@ -151,11 +151,11 @@ class Parser {
     }
 
     isNotEndOfBlock () {
-        return this.isNotEndOfFile() && (this.lexer().peek().value != constants.SYM.R_PAREN);
+        return this.isNotEndOfFile() && (this.lexer().peek().value !== constants.SYM.R_PAREN);
     }
 
     parseVarname () {
-        return (this.lexer().peek().type == constants.VARIABLE)
+        return (this.lexer().peek().type === constants.VARIABLE)
             ? this.lexer().next().value
             : this.lexer().throwError(this.getGenericErrorMsg(this.lexer().peek().value));
     }
@@ -189,7 +189,7 @@ class Parser {
     parseAst () {
         const token = this.lexer().peek();
 
-        if (kwnodes[token.value] != undefined) {
+        if (kwnodes[token.value]) {
             const kwNode = kwnodes[token.value];
             if (kwNode instanceof BaseNode) return kwNode.getNode.call(this); // call the method getNode in kwNode object like an extension function to the Parser class
             else throw new Error(`${kwNode} must be of type BaseNode`);