函数的默认值function add(a = 1, b = 2) {
return a + b
}
console.log(add())//3
console.log(add(10)) //12
console.log(add(10, 20)) //30
解构赋值数组解构let [a, b, c] = [1, 2, 3]
console.log(a, b, c)
let [a, b, c, d, e] = [1, 2, 3]
console.log(a, b, c, d, e)
对象解构let student = {
uname: 'james',
age: 13,
address: '洛杉矶'
}
let { uname, age, address } = student
console.log(uname, age, address)
//别名
let student = {
uname: 'james',
age: 13,
address: '洛杉矶'
}
let { uname: uName, age: uAge, address: uAddress } = student
console.log(uName, uAge, uAddress)剩余参数let add = (...arg) => {
let count = 0
arg.forEach(item => {
count += item
})
console.log(count)
}
add(1, 2, 3)
add(1, 2, 3, 4, 5, 6)剩余参数和解构let arr = [1, 3, 5, 7, 9]
// let [...a] = arr
// console.log(a)
// let [a, ...b] = arr
// console.log(a)
// console.log(b)
let [a, b, ...c] = arr
console.log(a)
console.log(b)
console.log(c)扩展运算符let arr = [1, 3, 5, 7, 9] // 1,3,5,7,9
console.log( ...arr )
//合并两个数组
//方式一
let arr1 = [1, 3]
let arr2 = [2, 5]
let newArr = [...arr1, ...arr2]
console.log(newArr)
//方式二
arr1.push(...arr2)
console.log(arr1)
// 伪数组转成真正的数组
let spans = document.getElementsByTagName('span')
spans = [...spans]
spans.forEach(function (item) {
console.log(item)
})
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