【相关学习推荐：javascript视频教程】
废话不多话，在本文中，列出了一些比较常用或者实用的的 JavaScript 代码片段，希望对你们有所帮助。
1.三元运算符
let someThingTrue = true
if(someThingTrue){
handleTrue()
}else{
handleFalse()
}
****** 以下是简短版本 ******
let someThingTrue = true
someThingTrue ? handleTrue() : handleFalse()复制代码2.短路或运算const defaultValue = "SomeDefaultValue" let someValueNotSureOfItsExistance = null let expectingSomeValue = someValueNotSureOfItsExistance || defaultValue console.log(expectingSomeValue) // SomeDefaultValue复制代码3. 条件成立
let someValue = true
if (someValue) {
console.log('条件成立!')
}复制代码4. for循环for (let i = 0; i < 1e2; i++) { // 代替 i<100 是不是有点酷
}复制代码let someValues = [1, 2, 4]
for (let val in someValues) {
console.log(val)
}
let obj = {
'key1': 'value1',
'key2': 'value2',
'key3': 'value3'
}
for (let key in obj) {
console.log(key)
}复制代码5. 值到对象的映射let x='x',y='y'
let obj = {x,y}
console.log(obj) // {x: "x", y: "y"}复制代码6. Object.entries()const credits = {
producer: '大迁世界',
name: '前端小智',
rating: 9
}
const arr = Object.entries(credits)
console.log(arr)
*** 输出 ***
[ [ 'producer', '大迁世界' ], [ 'name', '前端小智' ], [ 'rating', 9 ] ]复制代码7. Object.values()const credits = {
producer: '大迁世界',
name: '前端小智',
rating: 9
}
const arr = Object.values(credits)
console.log(arr)
*** 输出 ***
[ '大迁世界', '前端小智', 9 ]复制代码8. 模板字面量let name = '前端小智'
let age = 20
var someStringConcatenateSomeVariable = `我是 ${name}，今年 ${age} 岁`
console.log(someStringConcatenateSomeVariable)复制代码9. 解构赋值import { observable, action, runInAction } from 'mobx';复制代码10.多行字符串let multiLineString = `some string\\n with multi-line of\\n characters\\n` console.log(multiLineString)复制代码11.Array.find 简写
const pets = [{
type: 'Dog',
name: 'Max'
},
{
type: 'Cat',
name: 'Karl'
},
{
type: 'Dog',
name: 'Tommy'
}
]
pet = pets.find(pet => pet.type === 'Dog' && pet.name === 'Tommy')
console.log(pet) // { type: 'Dog', name: 'Tommy' }复制代码12.默认参数值早期的做法
function area(h, w) {
if (!h) {
h = 1;
}
if (!w) {
w = 1;
}
return h * w
}复制代码ES6 以后的做法
function area(h = 1, w = 1) {
return h * w
}复制代码13.箭头函数的简写let sayHello = (name) => {
return `你好，${name}`
}
console.log(sayHello('前端小智'))复制代码简写如下：
let sayHello = name => `你好，${name}`
console.log(sayHello('前端小智'))复制代码14.隐式返回let someFuncThatReturnSomeValue = (value) => {
return value + value
}
console.log(
someFuncThatReturnSomeValue('前端小智'))复制代码简写如下：
let someFuncThatReturnSomeValue = (value) => (
value + value
)
console.log(someFuncThatReturnSomeValue('前端小智'))复制代码15.函数必须有参数值function mustHavePatamMethod(param) {
if (param === undefined) {
throw new Error('Hey You must Put some param!');
}
return param;
}复制代码以像这样重写:
mustHaveCheck = () => {
throw new Error('Missing parameter!')
}
methodShoudHaveParam = (param = mustHaveCheck()) => {
return param
}复制代码16.charAt() 简写'SampleString'.charAt(0) // S // 简写 'SampleString'[0]复制代码17.有条件的函数调用
function fn1() {
console.log('I am Function 1')
}
function fn2() {
console.log('I am Function 2')
}
/*
长的写法
*/
let checkValue = 3;
if (checkValue === 3) {
fn1()
} else {
fn2()
}复制代码简短的写法：
(checkValue === 3 ? fn1 : fn2)()复制代码17.Math.Floor 简写
let val = '123.95' console.log(Math.floor(val)) // 常规写法 console.log(~~val) // 简写复制代码18.Math.pow 简写
Math.pow(2, 3) // 8 // 简写 2 ** 3 // 8复制代码19.将字符串转换为数字
const num1 = parseInt('100')
// 简写
console.log(+"100")
console.log(+"100.2")复制代码20.&& 运算let value = 1;
if (value === 1)
console.log('Value is one')
//OR In short
value && console.log('Value is one')复制代码21.toString 简写let someNumber = 123
console.log(someNumber.toString()) // "123"
// 简写
console.log(`${someNumber}`) // "123"复制代码22.可选的链运算符（即将发布 
