数组方法总结
Push方法:
添加一个新元素到数组尾部，并返回修改后数组的长度；
let arr1=[1,2,3,4,5,6,7,8,9]
this.arr1.push("A")
console.log(this.arr1) //1,2,3,4,5,6,7,8,9,A
Pop方法:
从数组最后方删除一个元素，并返回移除的项；
let arr1=[1,2,3,4,5,6,7,8,9]
this.arr1.pop()
console.log(this.arr1) //1,2,3,4,5,6,7,8
shift方法:
移除数组的第一个元素，并返回该项；
let arr1=[1,2,3,4,5,6,7,8,9]
this.arr1.shift()
console.log(this.arr1) //2,3,4,5,6,7,8,9
unshift方法:
数组前端添加一个新元素，并返回修改后的数组长度；
let arr1=[1,2,3,4,5,6,7,8,9]
this.arr1.unshift("A")
console.log(this.arr1) //A,1,2,3,4,5,6,7,8,9
splice方法:
删除数组中指定index的指定个元素
splice拥有三个参数
splice('从第几个开始删除','删除多少个','删除后的位置插入的元素')
实例 从第5个元素开始删除两个元素并插入元素A
let arr1=[1,2,3,4,5,6,7,8,9]
this.arr1.splice(4,2,"A")
console.log(this.arr1) //1,2,3 4,A,7,8,9
join方法:
仅接受一个参数，数组转化成字符串 并以 ( ) 内的参数进行分割
let arr1=["A1","B2","C3"];
this.arr1.join(",") // "A1","B2","C3"
concat方法:
在concat的( )中传入参数,使原数组在尾部新增元素, 多用于数组的合并
let arr1=["A1","B2","C3"];
this.arr1.concat("D4") //["A1","B2","C3","D4"];
let arr2=["E5","H6"]
this.arr1.concat(arr2)//["A1","B2","C3","D4","E5","H6"]
slice方法:
从原数组中按照下标提取出新的数组
-
slice拥有两个参数 ( "开始的下标" ,"结束的下标")
-
当slice("单个参数")是,即为从此下标开始到数组结束进行copy
-
当slice(0)即为复制原数组
let arr1=["A1","B2","C3","D4","E5","H6"]
this.arr1.slice(1,3) //["B2","C3","D4"];
this.arr1.slice(4) //["E5","H6"]
this.arr1.slice(0) //["A1","B2","C3","D4","E5","H6"]
every方法:
数组的每一项都进入条件函数中,当每一项的运算结果都为true时,则整个返回true
var arr1=["1","2","3","4","5","6"]
var arr2=arr1.every(function(item,index,array){
return item>3
});
console.log(arr2)// false ,因为1，2，3均返回false
some方法:
数组的每一项都进入条件函数中,当有一项的运算结果都为true时,则整个返回true
var arr1=["1","2","3","4","5","6"]
var arr2=arr1.some(function(item,index,array){
return item>5
});
console.log(arr2)// true ,因为6大于5 则返回true
filter方法:
数组的每一项都进入条件函数中,返回判定为true的元素,组成新的数组
var arr1=[1,2,3,2,5];
var arr2=arr1.filter(function(item,index,array){
return item>=3
});
console.log(arr2)// [3,5] 过滤掉了小于3的元素
map方法:
数组的每一项都进入条件函数中,返回的是每一项运行函数后的值,所新组成的数组，下标具有一一对应的关系
//数组中每一项都 ×5标签：总结,console,数组,let,arr2,arr1,方法,log From： https://www.cnblogs.com/Dollom/p/16823352.html
var arr1=[3,6,9];
var arr2=arr1.map(function(item,index,array){
return item*5
});
console.log(arr2)// [15,30,45]