Not much nonsense, in this article, I list some commonly used or practical JavaScript code snippets, I hope it will be helpful to you.
1. Ternary operator
let someThingTrue = true
if(someThingTrue){
handleTrue()
}else{
handleFalse()
}
****** 以下是简短版本 ******
let someThingTrue = true
someThingTrue ? handleTrue() : handleFalse()
2. Short circuit 或calculation
const defaultValue = "SomeDefaultValue"
let someValueNotSureOfItsExistance = null
let expectingSomeValue = someValueNotSureOfItsExistance || defaultValue
console.log(expectingSomeValue) // SomeDefaultValue
3. Condition satisfied
let someValue = true
if (someValue) {
console.log('条件成立!')
}
4. forLoop
for (let i = 0; i < 1e2; i++) { // 代替 i<100 是不是有点酷
}
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)
}
5. Value to object mapping
let x='x',y='y'
let obj = {x,y}
console.log(obj) // {x: "x", y: "y"}
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 ] ]
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 ]
8. Template literal
let name = '前端小智'
let age = 20
var someStringConcatenateSomeVariable = `我是 ${name}，今年 ${age} 岁`
console.log(someStringConcatenateSomeVariable)
9. Destructuring assignment
import { observable, action, runInAction } from 'mobx';
10. Multi-line string
let multiLineString = `some string\n
with multi-line of\n
characters\n`
console.log(multiLineString)
11.Array.find shorthand
const pets = [{
type: 'Dog',
name: 'Max'
},
{
type: 'Cat',
name: 'Karl'
},
{
type: 'Dog',
name: 'Tommy'
}
]
pet = pets.find(pet => pet.type === 'Dog' && pet.name === 'Tommy')
console.log(pet) // { type: 'Dog', name: 'Tommy' }
12. Default parameter values
Early practice
function area(h, w) {
if (!h) {
h = 1;
}
if (!w) {
w = 1;
}
return h * w
}
What to do after ES6
function area(h = 1, w = 1) {
return h * w
}
13. Shorthand for arrow function
let sayHello = (name) => {
return `你好，${name}`
}
console.log(sayHello('前端小智'))
The abbreviation is as follows:
let sayHello = name => `你好，${name}`
console.log(sayHello('前端小智'))
14. Implicit return
let someFuncThatReturnSomeValue = (value) => {
return value + value
}
console.log(
someFuncThatReturnSomeValue('前端小智'))
The abbreviation is as follows:
let someFuncThatReturnSomeValue = (value) => (
value + value
)
console.log(someFuncThatReturnSomeValue('前端小智'))
15. The function must have parameter values
function mustHavePatamMethod(param) {
if (param === undefined) {
throw new Error('Hey You must Put some param!');
}
return param;
}
To rewrite like this:
mustHaveCheck = () => {
throw new Error('Missing parameter!')
}
methodShoudHaveParam = (param = mustHaveCheck()) => {
return param
}
16.charAt() shorthand
'SampleString'.charAt(0) // S
// 简写
'SampleString'[0]
17. Conditional function call
function fn1() {
console.log('I am Function 1')
}
function fn2() {
console.log('I am Function 2')
}
/*
长的写法
*/
let checkValue = 3;
if (checkValue === 3) {
fn1()
} else {
fn2()
}
Short wording:
(checkValue === 3 ? fn1 : fn2)()
17.Math.Floor shorthand
let val = '123.95'
console.log(Math.floor(val)) // 常规写法
console.log(~~val) // 简写
18.Math.pow shorthand
Math.pow(2, 3) // 8
// 简写
2 ** 3 // 8
19. Convert string to number
const num1 = parseInt('100')
// 简写
console.log(+"100")
console.log(+"100.2")
20.&& Operation
let value = 1;
if (value === 1)
console.log('Value is one')
//OR In short
value && console.log('Value is one')
21.toString shorthand
let someNumber = 123
console.log(someNumber.toString()) // "123"
// 简写
console.log(`${someNumber}`) // "123"
22. Optional chain operator (coming soon????)
Now there is a new proposal about ECMAScript, which is worth knowing.
let someUser = {
name: 'Jack'
}
let zip = someUser?.address?.zip //可选链接，像 Swift
If zipShi undefined, no error is raised.
The syntax also supports function and constructor calls
let address = getAddressByZip.?(12345)
If getAddressByZipit is the function that calls it, otherwise, the expression will be undefinedcalculated in the form of.
23. Use objects to replace switch syntax
let fruit = 'banana';
let drink;
switch (fruit) {
case 'banana':
drink = 'banana juice';
break;
case 'papaya':
drink = 'papaya juice';
break;
default:
drink = 'Unknown juice!'
}
console.log(drink) // banana juice
Author: xor Translator: Front Ash Source: medium
Original: https://medium.com/javascript-in-plain-english/some-js-shortcuts-82bc2f56146e
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