1. let 與 const
let 聲明的變量只在 let 命令所在的代碼塊內(nèi)有效粟判。
const 聲明一個(gè)只讀的常量，一旦聲明，常量的值就不能改變奄侠。
2.標(biāo)簽?zāi)０遄址?/h1>
const name ="why"
const age =18
//1.基本用法
//1.1.ES6之前
//const info = "my name is" + name + ",",age is "+ age
//1.2.ES6之后
const info =`my name is ${name}, age is ${age}`
console.log(info)//my name is why, age is 18
//2.標(biāo)簽?zāi)０遄址挠梅? function foo(...args){
console.log("參數(shù):",args)
}
foo("why",18,1.88)//參數(shù): ['why', 18, 1.88]
foo`my name is ${name},age is ${age},height is ${1.88}`//參數(shù): [Array(4), 'why', 18, 1.88]
3.ES8 字符串填充方法 padStart padEnd
const minute ="5".padStart(2,0)
const second="6".padStart(2,0)
console.log(`${minute}:${second}`)
//結(jié)果 05:06
![]()
image.png
4.ES11瞬内，Nullish Coalescing Operator增加了空值合并操作符
const foo = ""
const result1 =foo||"默認(rèn)值"
const result2 = foo ??"默認(rèn)值"
console.log(result1)//默認(rèn)值
console.log(result2)//""
const name ="why"
const age =18
//1.基本用法
//1.1.ES6之前
//const info = "my name is" + name + ",",age is "+ age
//1.2.ES6之后
const info =`my name is ${name}, age is ${age}`
console.log(info)//my name is why, age is 18
//2.標(biāo)簽?zāi)０遄址挠梅? function foo(...args){
console.log("參數(shù):",args)
}
foo("why",18,1.88)//參數(shù): ['why', 18, 1.88]
foo`my name is ${name},age is ${age},height is ${1.88}`//參數(shù): [Array(4), 'why', 18, 1.88]
const minute ="5".padStart(2,0)
const second="6".padStart(2,0)
console.log(`${minute}:${second}`)
//結(jié)果 05:06
image.png
const foo = ""
const result1 =foo||"默認(rèn)值"
const result2 = foo ??"默認(rèn)值"
console.log(result1)//默認(rèn)值
console.log(result2)//""
