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  • js开发实用技巧

    String Skill

    时间对比

    const time1 = "2019-02-14 21:00:00";
    const time2 = "2019-05-01 09:00:00";
    const overtime = time1 > time2;
    // overtime => false

    格式化金钱

    const ThousandNum = num => num.toString().replace(/B(?=(d{3})+(?!d))/g, ",");
    const money = ThousandNum(20190214);
    // money => "20,190,214"

    随机生成ID

    const RandomId = len => Math.random().toString(36).substr(3, len);
    const id = RandomId(10);
    // id => "jg7zpgiqva"

    生成随机HEX色值

    const RandomColor = () => "#" + Math.floor(Math.random() * 0xffffff).toString(16).padEnd(6, "0");
    const color = RandomColor();
    // color => "#f03665"

    生成星级评分(可以直接设置节点内容为start,然后设置不同颜色)

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

    操作URL查询参数

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

    Number Skill

    取整

    const num1 = ~~ 1.69;
    const num2 = 1.69 | 0;
    const num3 = 1.69 >> 0;
    // num1 num2 num3 => 1 1 1

    补零

    const FillZero = (num, len) => num.toString().padStart(len, "0");
    const num = FillZero(169, 5);
    // num => "00169"

    转数值

    //只对null、""、false、数值字符串有效
    const num1 = +null;
    const num2 = +"";
    const num3 = +false;
    const num4 = +"169";
    // num1 num2 num3 num4 => 0 0 0 169

    时间戳

    const timestamp = +new Date("2019-02-14");
    // timestamp => 1550102400000

    精确小数

    const RoundNum = (num, decimal) => Math.round(num * 10 ** decimal) / 10 ** decimal;
    const num = RoundNum(1.69, 1);
    // num => 1.7

    判断奇偶

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

    取最小最大值

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

    生成范围随机数

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

    Boolean Skill

    短路运算符

    const a = d && 1; // 满足条件赋值:取假运算,从左到右依次判断,遇到假值返回假值,后面不再执行,否则返回最后一个真值
    const b = d || 1; // 默认赋值:取真运算,从左到右依次判断,遇到真值返回真值,后面不再执行,否则返回最后一个假值
    const c = !d; // 取假赋值:单个表达式转换为true则返回false,否则返回true

    判断数据类型

    //可判断类型: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 /g, "").replace(/]/g, "").toLowerCase();
        return type ? dataType === type : dataType;
    }
    DataType("young"); // "string"
    DataType(20190214); // "number"
    DataType(true); // "boolean"
    DataType([], "array"); // true
    DataType({}, "array"); // false

    是否为空数组

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

    是否为空对象

    const obj = {};
    const flag = DataType(obj, "object") && !Object.keys(obj).length;
    // flag => true

    满足条件时执行

    const flagA = true; // 条件A
    const flagB = false; // 条件B
    (flagA || flagB) && Func(); // 满足A或B时执行
    (flagA || !flagB) && Func(); // 满足A或不满足B时执行
    flagA && flagB && Func(); // 同时满足A和B时执行
    flagA && !flagB && Func(); // 满足A且不满足B时执行

    为非假值时执行

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

    数组不为空时执行

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

    对象不为空时执行

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

    函数退出代替条件分支退出

    if (flag) {
        Func();
        return false;
    }
    // 换成
    if (flag) {
        return Func();
    }

    switch/case使用区间

    const age = 26;
    switch (true) {
        case isNaN(age):
            console.log("not a number");
            break;
        case (age < 18):
            console.log("under age");
            break;
        case (age >= 18):
            console.log("adult");
            break;
        default:
            console.log("please set your age");
            break;
    }

    Array Skill

    克隆数组

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

    合并数组

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

    去重数组

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

    混淆数组

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

    清空数组

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

    截断数组

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

    交换赋值

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

    过滤空值

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

    异步累计

    async function Func(deps) {
        return deps.reduce(async(t, v) => {
            const dep = await t;
            const version = await Todo(v);
            dep[v] = version;
            return dep;
        }, Promise.resolve({}));
    }
    const result = await Func(); // 需在async包围下使用

    数组首部插入成员

    let arr = [1, 2]; // 以下方法任选一种
    arr.unshift(0);
    arr = [0].concat(arr);
    arr = [0, ...arr];
    // arr => [0, 1, 2]

    数组尾部插入成员

    let arr = [0, 1]; // 以下方法任选一种
    arr.push(2);
    arr.concat(2);
    arr[arr.length] = 2;
    arr = [...arr, 2];
    // arr => [0, 1, 2]

    统计数组成员个数

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

    结构数组成员嵌套

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

    解构数组成员别名

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

    解构数组成员默认值

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

    获取随机数组成员

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

    创建指定长度数组

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

    创建指定长度且值相等的数组

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

    reduce代替map和filter

    const _arr = [0, 1, 2];
    
    // map
    const arr = _arr.map(v => v * 2);
    const arr = _arr.reduce((t, c) => {
        t.push(c * 2);
        return t;
    }, []);
    // arr => [0, 2, 4]
    
    // filter
    const arr = _arr.filter(v => v > 0);
    const arr = _arr.reduce((t, c) => {
        c > 0 && t.push(c);
        return t;
    }, []);
    // arr => [1, 2]
    
    // map和filter
    const arr = _arr.map(v => v * 2).filter(v => v > 2);
    const arr = _arr.reduce((t, c) => {
        c = c * 2;
        c > 2 && t.push(c);
        return t;
    }, []);
    // arr => [4]

    Object Skill

    克隆对象

    const _obj = { a: 0, b: 1, c: 2 }; // 以下方法任选一种
    const obj = { ..._obj };
    const obj = JSON.parse(JSON.stringify(_obj));
    // obj => { a: 0, b: 1, c: 2 }

    合并对象

    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 }

    对象字面量

    const env = "prod";
    const link = {
        dev: "Development Address",
        test: "Testing Address",
        prod: "Production Address"
    }[env];
    // link => "Production Address"

    对象变量属性

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

    创建纯空对象

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

    删除对象无用属性

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

    解构对象属性嵌套

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

    解构对象属性别名

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

    解构对象属性默认值

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

    Function Skill

    函数自执行

    const Func = function() {}(); // 常用
    
    (function() {})(); // 常用
    (function() {}()); // 常用
    [function() {}()];
    
    + function() {}();
    - function() {}();
    ~ function() {}();
    ! function() {}();
    
    new function() {};
    new function() {}();
    void function() {}();
    typeof function() {}();
    delete function() {}();
    
    1, function() {}();
    1 ^ function() {}();
    1 > function() {}();

    隐式返回值

    //只能用于单语句返回值箭头函数,如果返回值是对象必须使用()包住
    const Func = function(name) {
        return "I Love " + name;
    };
    // 换成
    const Func = name => "I Love " + name;

    一次性函数

    //适用于运行一些只需执行一次的初始化代码
    function
    Func() { console.log("x"); Func = function() { console.log("y"); } }

    惰性载入函数

    //函数内判断分支较多较复杂时可大大节约资源开销
    function Func() {
        if (a === b) {
            console.log("x");
        } else {
            console.log("y");
        }
    }
    // 换成
    function Func() {
        if (a === b) {
            Func = function() {
                console.log("x");
            }
        } else {
            Func = function() {
                console.log("y");
            }
        }
        return Func();
    }

    检测非空参数

    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"

    字符串创建函数

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

    优雅处理错误信息

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

    优雅处理Async/Await参数

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

    优雅处理多个函数返回值

    function Func() {
        return Promise.all([
            fetch("/user"),
            fetch("/comment")
        ]);
    }
    const [user, comment] = await Func(); // 需在async包围下使用

    DOM Skill

    显示全部DOM边框

    //调试也买你元素边界时使用
    [].forEach.call($$("*"), dom => {
        dom.style.outline = "1px solid #" + (~~(Math.random() * (1 << 24))).toString(16);
    });

    自适应页面

    //页面基于一张设计图但需做多款机型自适应,元素尺寸使用rem进行设置
    function AutoResponse(width = 750) {
        const target = document.documentElement;
        target.clientWidth >= 600
            ? (target.style.fontSize = "80px")
            : (target.style.fontSize = target.clientWidth / width * 100 + "px");
    }

    过滤XSS

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

    存取LocalStorage

    //反序列化取,序列化存
    const love = JSON.parse(localStorage.getItem("love"));
    localStorage.setItem("love", JSON.stringify("I Love You"));
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  • 原文地址:https://www.cnblogs.com/chao202426/p/11525573.html
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