面向 Web 开发人员的 58 个 JavaScript 技巧

思米米的小笔记-
JavaScript
本文最后更新于 1 年前，文中所描述的信息可能已发生改变。

作为程序员，编写代码也需要大量的写作技巧。好的代码可以让人耳目一新、通俗易懂、舒适自然，同时又充满成就感。因此，整理了一些近三年使用过的JS开发技巧，希望能让大家写出耳目一新、通俗易懂、舒适自然的代码。

字符串技巧

1: Compare time 

const time1 = "2022-03-02 09:00:00";
const time2 = "2022-03-02 09:00:01";
const overtime = time1 < time2;
// overtime => true

2: Format money 

const ThousandNum = num => num.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
const money = ThousandNum(1000000);
// money => '1,000,000'

3: Generate random ID 

const RandomId = len => Math.random().toString(36).substr(3, len);
const id = RandomId(10);
// id => "xdeguewg1f"

4: Generate random HEX color values 

const RandomColor = () => "#" + Math.floor(Math.random() * 0xffffff).toString(16).padEnd(6, "0");
const color = RandomColor();
// color => "#2cbf89"

5: Generate star ratings 

const StartScore = rate => "★★★★★☆☆☆☆☆".slice(5 - rate, 10 - rate);
const start = StartScore(3);
// start => '★★★☆☆'

6: URL query parameters 

const params = new URLSearchParams(location.search.replace(/\?/ig, "")); // location.search = "?name=test&sex=man"
params.has("test"); // true
params.get("sex"); // "man"

数字技巧

7: Arrangement 

const num1 = ~~1.19;
const num2 = 2.29 | 0;
const num3 = 3.09 >> 0;
// num1 num2 num3 => 1 2 3

8: Zero padding 

const FillZero = (num, len) => num.toString().padStart(len, "0");
const num = FillZero(1234, 5);
// num => "01234"

9: Revolution value 

const num1 = +null;
const num2 = +"";
const num3 = +false;
const num4 = +"169";
// num1 num2 num3 num4 => 0 0 0 169

10: Timestamp 

const timestamp = +new Date("2022-03-22");
// timestamp => 1647907200000

11: Exact decimal 

const RoundNum = (num, decimal) => Math.round(num * 10 ** decimal) / 10 ** decimal;
const num = RoundNum(1.2345, 2);
// num => 1.23

12: Parity 

const OddEven = num => !!(num & 1) ? "odd" : "even";
const num = OddEven(2);
// num => "even"

13: Take min max 

const arr = [0, 1, 2, 3];
const min = Math.min(...arr);
const max = Math.max(...arr);
// min max => 0 3   (0, 1, 2, 3)

14: Generate range random numbers 

const RandomNum = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min;
const num = RandomNum(1, 10); // 5

布尔技巧

15: Short-circuit operator 

const a = d && 1; // Fake operation, judge from left to right, return a false value when encountering a false value, and no longer execute it later, otherwise return the last true value
const b = d || 1; // Take the true operation, judge from left to right, return the true value when encountering the true value, and do not execute it later, otherwise return the last false value
const c = !d; // Returns false if a single expression converts to true, otherwise returns true

16: Determine the data type

可确定的类型：undefined、null、string、number、boolean、array、object、symbol、date、regexp、function、asyncfunction、arguments、set、map、weakset、weakmap

function DataType(tgt, type) {
    const dataType = Object.prototype.toString.call(tgt).replace(/\[object (\w+)\]/, "$1").toLowerCase();
    return type ? dataType === type : dataType;
}

DataType("test"); // "string"
DataType(20220314); // "number"
DataType(true); // "boolean"
DataType([], "array"); // true
DataType({}, "array"); // false

17: Check if array is empty 

const arr = [];
const flag = Array.isArray(arr) && !arr.length;
// flag => true

18: Execute when conditions are met 

const flagA = true; // Condition A
const flagB = false; // Condition B
(flagA || flagB) && Func(); // Execute when A or B is satisfied
(flagA || !flagB) && Func(); // Execute when A is satisfied or B is not satisfied
flagA && flagB && Func(); // Execute when both A and B are satisfied
flagA && !flagB && Func(); // Execute when A is satisfied and B is not satisfied

19: Executed if non-false 

const flag = false; // undefined、null、""、0、false、NaN
!flag && Func();

20: Executed when the array is not empty 

const arr = [0, 1, 2];
arr.length && Func();

21: Executed when the object is not null 

const obj = {a: 0, b: 1, c: 2};
Object.keys(obj).length && Func();

数组技巧

22: Clone array 

const _arr = [0, 1, 2];
const arr = [..._arr];
// arr => [0, 1, 2]

23: Merge array 

const arr1 = [0, 1, 2];
const arr2 = [3, 4, 5];
const arr = [...arr1, ...arr2];
// arr => [0, 1, 2, 3, 4, 5];

24: Deduplicated array 

const arr = [...new Set([0, 1, 1, null, null])];
// arr => [0, 1, null]

25: Obfuscated array 

const arr = [0, 1, 2, 3, 4, 5].slice().sort(() => Math.random() - .5);
// arr => [3, 4, 0, 5, 1, 2]

26: Empty an array 

const arr = [0, 1, 2];
arr.length = 0;
// arr => []

27: Truncate array 

const arr = [0, 1, 2];
arr.length = 2;
// arr => [0, 1]

28: Exchange assignment 

let a = 0;
let b = 1;
[a, b] = [b, a];
// a b => 1 0

29: Filter empty values

Empty values: undefined,null,””,0,false,NaN

const arr = [undefined, null, "", 0, false, NaN, 1, 2].filter(Boolean);
// arr => [1, 2]

30: Insert member at the beginning of the array 

let arr = [1, 2];
arr.unshift(0);
arr = [0].concat(arr);
arr = [0, ...arr];
// arr => [0, 1, 2]

31: Insert members at the end of the array 

let arr = [0, 1];
arr.push(2);
arr.concat(2);
arr[arr.length] = 2;
arr = [...arr, 2];
// arr => [0, 1, 2]

32: Count number of array members 

const arr = [0, 1, 1, 2, 2, 2];
const count = arr.reduce((t, v) => {
    t[v] = t[v] ? ++t[v] : 1;
    return t;
}, {});
// count => { 0: 1, 1: 2, 2: 3 }

33: Destructuring nested array members 

const arr = [0, 1, [2, 3, [4, 5]]];
const [a, b, [c, d, [e, f]]] = arr;
// a b c d e f => 0 1 2 3 4 5

34: Destructuring array member aliases 

const arr = [0, 1, 2];
const {0: a, 1: b, 2: c} = arr;
// a b c => 0 1 2

35: Destructuring array member default value 

const arr = [0, 1, 2];
const [a, b, c = 3, d = 4] = arr;
// a b c d => 0 1 2 4

36: Get random array member 

const arr = [0, 1, 2, 3, 4, 5];
const randomItem = arr[Math.floor(Math.random() * arr.length)];
// randomItem => 1

37: Create an array of specified length 

const arr = [...new Array(3).keys()];
// arr => [0, 1, 2]

38: Creates an array of the specified length and equal values 

const arr = new Array(3).fill(0);
// arr => [0, 0, 0]

对象技巧

39: Clone object 

const _obj = {a: 0, b: 1, c: 2};
const obj = {..._obj};
const obj = JSON.parse(JSON.stringify(_obj));
// obj => { a: 0, b: 1, c: 2 }

40: Merge objects 

const obj1 = {a: 0, b: 1, c: 2};
const obj2 = {c: 3, d: 4, e: 5};
const obj = {...obj1, ...obj2};
// obj => { a: 0, b: 1, c: 3, d: 4, e: 5 }

41: Object Variable Properties 

const flag = false;
const obj = {
    a: 0,
    b: 1,
    [flag ? "c" : "d"]: 2
};
// obj => { a: 0, b: 1, d: 2 }

42: Create a pure empty object 

const obj = Object.create(null);
Object.prototype.a = 0;
// obj => {}

43: Delete object useless properties 

const obj = {a: 0, b: 1, c: 2};
const {a, ...rest} = obj;
// rest => { b: 1, c: 2 }

44: Destructuring object property nesting 

const obj = {a: 0, b: 1, c: {d: 2, e: 3}};
const {c: {d, e}} = obj;
// d e => 2 3

45: Destructuring object property aliases 

const obj = {a: 0, b: 1, c: 2};
const {a, b: d, c: e} = obj;
// a d e => 0 1 2

46: Destructuring object property default values 

const obj = {a: 0, b: 1, c: 2};
const {a, b = 2, d = 3} = obj;
// a b d => 0 1 3

函数技巧

47: Function self-execution 

const Func = function () {
}(); // Commonly used
(function () {
})(); // Commonly used
(function () {
}()); // Commonly used
[function () {
}()];

+function () {
}();

-function () {
}();
~function () {
}();
!function () {
}();
new function () {
};
new function () {
}();
void function () {
}();
typeof function () {
}();
delete function () {
}();
1, function () {
}();
1 ^ function () {
}();
1 > function () {
}();

48: One-time function

适合运行一些只需要执行一次的初始化代码，如：

function Func() {
    console.log("x");
    Func = function () {
        console.log("y");
    }
}

49: Lazy loading functions

当函数中的复杂判断分支越来越多时，可以大大节省资源开销，可以使用闭包来实现。

function Func() {
    if (a === b) {
        console.log("x");
    } else {
        console.log("y");
    }
}

// replace with
function Func() {
    if (a === b) {
        Func = function () {
            console.log("x");
        }
    } else {
        Func = function () {
            console.log("y");
        }
    }
    return Func();
}

50: Detect non-null parameters 

function IsRequired() {
    throw new Error("param is required");
}

function Func(name = IsRequired()) {
    console.log("I Love " + name);
}

Func(); // "param is required"
Func("You"); // "I Love You"

51: String creation function 

const Func = new Function("name", "console.log(\"I Love \" + name)");

52: Handle error messages gracefully 

try {
    Func();
} catch (e) {
    location.href = "https://stackoverflow.com/search?q=[js]+" + e.message;
}

53: Handle Async/Await parameters gracefully 

function AsyncTo(promise) {
    return promise.then(data => [null, data]).catch(err => [err]);
}

const [err, res] = await AsyncTo(Func());

54: Handle multiple function return values gracefully 

function Func() {
    return Promise.all([
        fetch("/user"),
        fetch("/comment")
    ]);
}

const [user, comment] = await Func();

DOM技巧

55: Show all DOM borders 

[].forEach.call($("*"), dom => {
    dom.style.outline = "1px solid #" + (~~(Math.random() * (1 << 24))).toString(16);
});

56: Responsive pages

页面基于设计图但需要适配多个模型，元素大小使用rem设置

function AutoResponse(width = 750) {
    const target = document.documentElement;
    target.clientWidth >= 600
        ? (target.style.fontSize = "80px")
        : (target.style.fontSize = target.clientWidth / width * 100 + "px");
}

57: Filter XSS 

function FilterXss(content) {
    let elem = document.createElement("div");
    elem.innerText = content;
    const result = elem.innerHTML;
    elem = null;
    return result;
}

58: Access LocalStorage 

const love = JSON.parse(localStorage.getItem("love"));
localStorage.setItem("love", JSON.stringify("I Love You"));
在VScode中使用Babel ES6转ES5
前端开发规范：命名规范、html规范、css规范、js规范