1var-let-const
a =3
var a
var a = 4
a =3
let a
let a =3
let a= 4
let a= 5
for(leti =0; i<3;i++ ){
console.log(i)
}
console.log(i)
const a =1
a=2
const obj ={a:1}
obj.a =2
obj{a:2}
2解构赋值
let [a,b,c] =[1,2,3]
console.log(a,b,c)
let {a,{b},c} =[2,[3],4]
a
b
c
let[a] =1
let[a,b=2] =[3,4]
a
b
let [a=2, b=3] =[undefined, null]
a
b
let[a=1,b=a] =[2]
a
b
let [name, age] =['hunger',3]
let p1 ={name,age}
let p2 ={name:name,age:age}
let {name,age} ={name:'ha', age:4}
let name
let age
{{name:name,age:age}={name:'ha',age:4}}
let{x,y=5}={x:1}
x
y
functon add([x=1,y=2]){
return x+y
}
add()
add([2])
add([3,4])
function sum{{x,y}={x:0,y:0},{a=1,b=1}}{
return [x+a, y+b]
}
sum{{x:1,y:2},{a:2}}
let[x,y] =[1,2]
[x,y]= [y,x]
x
y
3 字符串-函数-数组-对象
字符串
let str = `
hi,
This is ha.com.
You are very good
`
let website = 'ha'
let who ='you'
let str =`
this is ${website}.
${who} are very good
`
数组
var a =[1,2]
console.log(...a)
var b =[...a,3]
b
function sort(...arr){
console.log(arr.sort())
}
sort(3,1,5)
let ps =document.querySelectorAll('p');
Array.from(ps).forEach(p=>{
consoloe.log(p.innerText);
});
[...ps].forEach(p=>{console.log(p.innerText)});
函数
function sayHi(name='ha'){
console.log(`hi,${name}`)
}
sayHi()
sayHi('good')
模块化