var arr=[1,2,3,4,5];

數(shù)組常用的api

pop

刪除原數(shù)組最后一項(xiàng)，并返回刪除元素的值；如果數(shù)組為空則返回undefined

var a = [1,2,3,4,5]; 
var b = a.pop(); //a：[1,2,3,4]   b：5 //不用返回的話直接調(diào)用就可以了

push

將參數(shù)添加到原數(shù)組末尾，并返回?cái)?shù)組的長(zhǎng)度

var a = [1,2,3,4,5]; 
var b = a.push(6,7); //a：[1,2,3,4,5,6,7]   b：7 

concat

返回一個(gè)新數(shù)組，是將參數(shù)添加到原數(shù)組中構(gòu)成的

var a = [1,2,3,4,5]; 
var b = a.concat(6,7); //a：[1,2,3,4,5]   b：[1,2,3,4,5,6,7] 

splice(start,deleteCount,val1,val2,...)

從start位置開(kāi)始刪除deleteCount項(xiàng)，并從該位置起插入val1,val2,...

var a = [1,2,3,4,5]; 
var b = a.splice(2,2,7,8,9); //a：[1,2,7,8,9,5]   b：[3,4] 
var b = a.splice(0,1); //同shift 
a.splice(0,0,-2,-1); var b = a.length; //同unshift 
var b = a.splice(a.length-1,1); //同pop 
a.splice(a.length,0,6,7); var b = a.length; //同push 

reverse

將數(shù)組反序

var a = [1,2,3,4,5]; 
var b = a.reverse(); //a：[5,4,3,2,1]   b：[5,4,3,2,1] 

sort(orderfunction)

按指定的參數(shù)對(duì)數(shù)組進(jìn)行排序

var a = [1,2,3,4,5]; 
var b = a.sort(); //a：[1,2,3,4,5]   b：[1,2,3,4,5] 

slice(start,end)

返回從原數(shù)組中指定開(kāi)始下標(biāo)到結(jié)束下標(biāo)之間的項(xiàng)組成的新數(shù)組

var a = [1,2,3,4,5]; 
var b = a.slice(2,5); //a：[1,2,3,4,5]   b：[3,4,5] 

join(separator)

將數(shù)組的元素組起一個(gè)字符串，以separator為分隔符，省略的話則用默認(rèn)用逗號(hào)為分隔符

var a = [1,2,3,4,5]; 
var b = a.join("|"); //a：[1,2,3,4,5]   b："1|2|3|4|5"

forEach

arr.forEach(function(item,index){
    console.log(item);
});

map

var newArr= arr.map(function(item,index){
    return item*2;
});

filter

var newArr= arr.filter(function(item,index){
    return item>3;
});

reduce

(讓數(shù)組中的前項(xiàng)和后項(xiàng)做某種計(jì)算，并累計(jì)最終值)

var result= arr.reduce(function(prev,next){
    return prev+next;
});

every

檢測(cè)數(shù)組中每項(xiàng)是否符合

var result=arr.every(function(item,index){
    return item>0;
});
//true

some

檢測(cè)數(shù)組中是否有某些項(xiàng)符合條件

var result= arr.some(function(item,index){
    return item>1;
});