目录
取整：代替正数的Math.floor()，代替负数的Math.ceil()
过滤空值：undefined、null、""、0、false、NaN
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
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
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
获取随机数组
getRandomArr: function (length, min, max) {
var arr = new Array(length);
for (var i = 0; i < arr.length; i++) {
arr[i] = Math.random() * (max - min) + min
}
return arr;
}String Skill
时间对比：时间个位数形式需补0
const time1 = "2019-03-31 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(19941112);
// money => "19,941,112"
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=yajun&sex=female"
params.has("yajun"); // true
params.get("sex"); // "female"
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 => 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("2019-03-31");
// timestamp => 1553990400000
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：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("yajun"); // "string"
DataType(19941112); // "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：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 }
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 = [...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：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("雅君妹纸"); // "I Love 雅君妹纸"
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) {
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 雅君妹纸"));