var a =[1,2,3]var b = a.slice(0,1)// 不填参数则表示剪切整个数组 var c = a.slice()
console.log(a)// [1,2,3]
console.log(b)// [1]
console.log(c)// [1,2,3]
console.log(a===c)// false // 注意 a !== c// 负数表示从后往前数var d = a.slice(-1,-2)
console.log(d)// [] 从左向右截取,所以说为[]var e = a.slice(-1)
console.log(e)// [3]
8.join()不改变原数组,返回转换后的字符串
join() 方法用来将数组转换为字符串
var a =[1,2,3,4,5]
console.log(a.join(','))// 1,2,3,4,5
console.log(a)// [1,2,3,4,5]
9.sort() 排序 改变原数组,返回排序后的数组
var a =['a','b','d','c']
console.log(a.sort())// ['a','b','c','d']
console.log(a)// ['a','b','c','d']
10.reverse() 颠倒顺序 返回的是颠倒后的数组,会改变原数组。
reverse() 方法用于颠倒数组中元素的顺序。
var a =[1,3,2,7,6]
console.log(a.reverse())// [6,7,2,3,1]
console.log(a)// [6,7,2,3,1]
var a =[1,2,3,4,11]// 第一个参数为一个方法,有三个参数,current:当前值 index:当前值下标 array:这个数组对象var b = a.filter(function(current,index,array){return current <10})
console.log(b)// [1,2,3,4]
console.log(a)// [1,2,3,4,11]
var a =[1,2,3,4,5]// 参数同filter方法var b = a.map(function(current,index,array){return current +1})
console.log(b)// [2,3,4,5,6]
console.log(a)// [1,2,3,4,5]
14.every() 对数组的每一项都运行给定的函数,若每一项都返回 ture,则返回 true
var a =[1,2,3,4,5]var b = a.every(function(current,index,array){return current <6})var c = a.every(function(current,index,array){return current <3})
console.log(b)// true
console.log(c)// false
var a =[1,2,3,4,5]var b = a.some(function(current,index,array){return current >4})var c = a.some(function(current,index,array){return current >5})
console.log(b)// true
console.log(c)// false
16.forEach() 数组遍历 遍历整个数组,中途不能中断
var arr =['a','b','c']var copy =[]
arr.forEach(function(item){
copy.push(item)})
console.log(copy)