feat(find): a function that finds the first element that matches the predicate in an array (#134)

This method will iterate over elements of an array, returning the first element that the given

predicate returns truthy for.

Closes #133

Author: hmch17

src/find.js

@@ -0,0 +1,28 @@
+export default find
+
+/**
+ * This method will iterate over elements of an array, returning the first element
+ * that the given predicate returns truthy for.
+ * Similar to _.find in LoDash https://lodash.com/docs/4.17.4#find
+ *
+ * @param {Array} array - Input array of objects
+ * @param {Function} predicate - A function that iterates over the elements in `array`
+ * @return {Object} - First element that matches the predicate
+ */
+
+function find(array, predicate) {
+  if (!(array instanceof Array)) {
+    return undefined
+  }
+
+  let foundElement
+
+  for (let i = 0; i < array.length; i++) {
+    if (predicate(array[i])) {
+      foundElement = array[i]
+      return foundElement
+    }
+  }
+
+  return undefined
+}

src/index.js

@@ -47,13 +47,15 @@ import range from './range'
 import contains from './contains'
 import getOrdinalSuffix from './get-ordinal-suffix'
 import arrayAverage from './array-average'
+import find from './find'
 
 export {
   isOdd,
   isEven,
   revstring,
   initArray,
   reduce,
+  find,
   flatten,
   snakeToCamel,
   getQueryStringParam,

test/find.test.js

@@ -0,0 +1,26 @@
+import test from 'ava'
+import { find } from '../src'
+
+test('find returns undefined if the input is not an instance of Array', t => {
+  const original = { prop: 'test' }
+  const predicate = element => 'does nothing'
+  const expected = undefined
+  const actual = find(original, element => predicate(element))
+  t.deepEqual(actual, expected)
+})
+
+test('find returns the first element that matches the given predicate', t => {
+  const original = [{ a: 1, b: 2 }, { c: 3 }, { a: 1, c: 4 }]
+  const predicate = element => element.a === 1
+  const expected = { a: 1, b: 2 }
+  const actual = find(original, element => predicate(element))
+  t.deepEqual(actual, expected)
+})
+
+test('find returns undefined if nothing matches the given predicate', t => {
+  const original = [{ a: 1, b: 2 }, { c: 3 }, { a: 1, c: 4 }]
+  const predicate = element => element.d === 1
+  const expected = undefined
+  const actual = find(original, element => predicate(element))
+  t.deepEqual(actual, expected)
+})