谈谈JavaScript数组常用方法总结

var arr=[1,2,3]; 
//从末尾增加 
arr.push(4); 
console.log(arr);//[1,2,3,4] 
 
//从前端增加 
arr.unshift(0); 
console.log(arr);//[0,1,2,3,4] 

var arr=[1,2,3]; 
//从末尾删除 
arr.pop(); 
console.log(arr);//[1,2] 
 
//从前端删除 
arr.unshift(); 
console.log(arr);//[2] 

var arr=[1,2,3,4,5]; 
var deleteArr=arr.splice(1,2,8,9); 
 
console.log(deleteArr);//[2,3] 
console.log(arr);//[1,8,9,4,5] 

var arr=[1,2,3]; 
arr.reverse(); 
console.log(arr);//[3,2,1] 

var arr=[1,2,3]; 
arr.join(','); 
console.log(arr);//1,2,3 

var arr1=[1,2,3]; 
var arr2=[4,5,6]; 
 
var newArr=arr1.concat(arr2); 
 
console.log(arr1);//[1,2,3] 
console.log(arr2);//[4,5,6] 
console.log(newArr);//[1,2,3,4,5,6] 

var arr=[3,5,1]; 
 
arr.sort(); 
 
console.log(arr);//[1,3,5]; 
 
//指定降序 
var arr1=[4,2,7]; 
arr1.sort(function(a,b){ 
  return b-a; 
}) 
console.log(arr1);//[7,4,2] 

var arr=[1,2,3,4,5,6]; 
 
var newArr=arr.slice(1,3); 
 
console.log(arr);//[1,2,3,4,5,6] 
console.log(newArr);//[2,3] 

var arr=[1,2,3]; 
 
var loc=arr.indexOf(1); 
console.log(loc);//0 
 
var newLoc=arr.indexOf(4); 
console.log(newLoc);//-1 

var arr=[1,2,3]; 
 
//index是索引，value是值 
arr.forEach(function(value,index,arr){ 
   console.log(''index:"+index+" "+"value:"+value) 
}) 

var arr=[1,2,3,4]; 
 
//返回数组中大于2的内容 
var newArr=arr.filter(function(item){ 
  return item>2; 
}) 
 
console.log(arr);//[1,2,3,4] 
console.log(newArr);//[3,4] 

var arr=[1,2,3,4]; 
 
//将数组每个值扩大一倍 
var newArr=arr.map(function(item){ 
  return item*2; 
}); 
 
console.log(arr);//[1,2,3,4] 
console.log(newArr);//[2,4,6,8]