var arr=new Array(); 
arr[0]=“11”; 
arr[1]=“22”; 
arr[2]=“33”; 

var arr=new Array(“11”,“22”,“33”); 

var arr=[“11”,“22”,“33”]; 

var arr=[“11″,”22″,”33″]; 
arr.length //3，返回数组的长度 
arr.length = 2 //['11','22']，截取数组前2个 
arr.length = 5 //['11','22',undefined,undefined,undefined]，自动添加undefined 
arr.length = 0 //[]，清空数组 

var arr=[“11”,“22”,“33”]; 
//for循环 
for(var i=0;i<arr.length;i++){ 
 console.log(i) 
} 
//for in循环 
for( i in arr ){ 
 console.log(arr[i]) 
} 
//forEach循环 
arr.forEach(function(i){ 
 console.log(i) 
}) 

var arr=[1,2,3]; 
arr.push(4) 
console.log(arr) //[1,2,3,4] 
arr.push(5,6,7) 
console.log(arr) //[1,2,3,4,5,6,7] 

var arr=[1,2,3]; 
arr.unshift(4) 
console.log(arr) //[4,1,2,3] 
arr.unshift(5,6,7) 
console.log(arr) //[5,6,7,1,2,3,4] 

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

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

var arr=[1,2,3,4]; 
arr.join(‘-‘) //”1-2-3-4″ 
arr.join(”) //”1234″ 
arr.join(‘ ‘) //”1 2 3 4″ 

var arr=[2,8,3,4,12,56]; 
//从小到大排序 
arr.sort(function(a,b){ 
 return a-b; 
}); 
//从大到小排序 
arr.sort(function(a,b){ 
 return b-a; 
}); 
//随机排序 
arr.sort(function(a,b){ 
 return Math.random() – 0.5 
}) 

var arr=[2,8,3,4,12,56]; 
arr.reverse() //[56, 12, 4, 3, 8, 2] 

var arr = [5, 458 , 120 , -215 , 228 , 400]; 
var max = Math.max.apply(Math, arr); 
var min = Math.min.apply(Math, arr); 

var arr=[2,8,3,4,12,56]; 
arr.slice(1) //[8, 3, 4, 12, 56] 
arr.slice(1,5) //[8, 3, 4, 12] 

var arr=[2,8,3,4,12,56]; 
//从下标2的位置开始截取 
console.log(arr.splice(2)) // [3, 4, 12, 56] 
console.log(arr)  // [2, 8] 
 
var arr=[2,8,3,4,12,56]; 
//删除下标1到5的位置 
console.log(arr.splice(1,5)) //[8, 3, 4, 12, 56] 
console.log(arr)  // [2] 
 
var arr=[2,8,3,4,12,56]; 
//替换下标1的位置 
console.log(arr.splice(1,1,'qqq')) //[8] 
console.log(arr) //[2, “qqq”, 3, 4, 12, 56] 
 
var arr=[2,8,3,4,12,56]; 
//把下标1到3的位置删除，并插入qqq 
console.log(arr.splice(1,3,'qqq')) //[8, 3, 4] 
console.log(arr) // [2, “qqq”, 12, 56] 

var arr1=[1,2,3,4,5]; 
var arr2=[6,7]; 
var arr3=arr1.concat(arr2); 
alert(arr1);// [1,2,3,4,5] 
alert(arr2);// [6,7] 
alert(arr3);// [1,2,3,4,5,6,7] 

function removeRepeat(arr){ 
 return arr.filter(function(elem, pos) { 
  return arr.indexOf(elem) == pos; 
 }); 
} 

function removeRepeat(a){ 
 var arr=[]; 
 for(var i=0;i<a.length;i++){ 
  if(arr.indexOf(a[i]) === -1){ 
   arr.push(a[i]); 
  } 
 } 
 return arr; 
} 

function removeRepeat(a){ 
 var arr = []; 
 a.forEach(function(i){ 
   if(arr.indexOf(i) === -1){ 
   arr.push(i); 
  } 
 }); 
 return arr 
} 

function removeRepeat(arrs){ 
 var newArr = []; 
 var hash = {}; 
 for(var i=0;i<arrs.length;i++){ 
  var key = typeof(arrs[i])+arrs[i]; 
  if(hash[key] !==1){ 
   newArr.push(arrs[i]); 
   hash[key] =1; 
  };  
 }; 
 return newArr; 
} 

//比如我们给数组添加一个求和的方法 
Array.prototype.sum= function(){ 
 var n = 0; 
 this.forEach(function(i){ 
  n+=i; 
 }); 
 return n; 
} 
 
var arr = [1,2,3,4] 
alert(arr.sum()) //10