validNumber.js

var isNumber = function (s) {
    /**
     * blank    空格
     * sign     + -
     * digit    0-9
     * e        e
     * .        .
     */
    const graph = {
        0: { blank: 0, sign: 1, ".": 2, digit: 6 },
        1: { digit: 6, ".": 2 },
        2: { digit: 3 },
        3: { digit: 3, e: 4 },
        4: { digit: 5, sign: 7 },
        5: { digit: 5 },
        6: { digit: 6, ".": 3, e: 4 },
        7: { digit: 5 },
    };

    let state = 0;

    for (let c of s.trim()) {
        if (c >= '0' && c <= '9') {
            c = 'digit';
        } else if (c === ' ') {
            c = 'blank';
        } else if (c === '+' || c === '-') {
            c = 'sign';
        }
        // 如果得到的当前节点为 undefined 说明不在可用字符范围，直接返回false
        if (graph[state] === undefined) return false;
        state = graph[state][c];
        // 如果得到的状态为 undefined 说明不在可用字符范围，也直接返回false
        if (state === undefined) return false;
    }

    // 走到红色节点就为true
    if ([3, 5, 6].includes(state)) {
        return true;
    }
    return false;
};