你可能不知道的JS开发技巧

String Skill

对比时间

❝时间个位数形式需补0
❞

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"

生成随机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

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"); // trueparams.get("sex"); //"male"

Number Skill

取整

❝代替正数的Math.floor()，代替负数的Math.ceil()
❞

const num1 = ~~ 1.69;const num2 = 1.69 | 0;const num3 = 1.69 >> 0;// num1 num2 num3 => 111

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 = +newDate("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";constnum = OddEven(2);// num => "even"

取最小最大值

const arr = [0, 1, 2];constmin = Math.min(...arr);constmax = Math.max(...arr);// minmax => 02

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(/\[object (\w+)\]/, "$1").toLowerCase(); return type ? dataType === type : dataType;}DataType("young"); //"string"DataType(20190214); //"number"DataType(true); //"boolean"DataType([], "array"); // trueDataType({}, "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Aconst 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(); returnfalse;}// 换成if(flag) { returnFunc();}

switch/case使用区间

const age = 26;switch (true) { caseisNaN(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 = [...newSet([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

asyncfunctionFunc(deps) { return deps.reduce(async(t, v) => { const dep = await t; const version = awaitTodo(v); dep[v] = version; return dep; }, Promise.resolve({}));}const result = awaitFunc(); // 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, v) => { t[v] = t[v] ? ++t[v] :1; return t;}, {});// count => { 0:1, 1:2, 2:3 }

解构数组成员嵌套

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

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

创建指定长度且值相等的数组

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

reduce代替map和filter

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

❝获取环境变量时必用此方法，用它一直爽，一直用它一直爽
❞

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cconst { 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 => 23

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 => 012

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 => 013

Function Skill

函数自执行

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
❞

functionFunc() { 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
❞

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

检测非空参数

function IsRequired() { thrownewError("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

constFunc = newFunction("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

functionAsyncTo(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() { returnPromise.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

❝调试页面元素边界时使用
❞

[].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){ consttarget = document.documentElement; target.clientWidth >= 600 ? (target.style.fontSize = "80px") : (target.style.fontSize = target.clientWidth / width * 100 + "px");}

过滤XSS

function FilterXss(content) { letelem = 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"));

总结

写到最后总结得差不多了，如果后续我想起还有哪些遗漏的「JS开发技巧」，会继续在这篇文章上补全。

最后送大家一个键盘！

(_=>[..."`1234567890-=~~QWERTYUIOP[]\\~ASDFGHJKL;'~~ZXCVBNM,./~"].map(x=>(o+=`/${b='_'.repeat(w=x<y?2:' 667699'[x=["Bs","Tab","Caps","Enter"][p++]||'Shift',p])}\\|`,m+=y+(x+' ').slice(0,w)+y+y,n+=y+b+y+y,l+=' __'+b)[73]&&(k.push(l,m,n,o),l='',m=n=o=y),m=n=o=y='|',p=l=k=[])&&k.join``)()