javascriptの配列Aray

var a=new Array();
console.log(a);
a=new Array(3);
console.log(a);//   3   
a=new Array("abc","xyz");
console.log(a);
//  ，     
a=Array(3);
a=Array("abc","xyz");
//      
a=[];
a=[3];
a=["abc","xyz"];
console.log(a.length);//     
console.log(a[1]);//        
a.length=1;//    
console.log(a[1]);//undefined
a[a.length]="asd";//        asd
console.log(a);//  
a[a.length]="zxc";//     
console.log(a);//  
a=["0","1","2"];
a[99]=99;//   100  99
console.log(a.length);//   100
console.log(a[4]);//undefined,         

a=["qwe","asd","zxc"];
console.log(a instanceof Array);//       ，         BUG
console.log(Array.isArray(a));//      ，         ，IE8           

console.log(a.toString());//qwe,asd,zxc
console.log(a.valueOf());//["qwe","asd","zxc"]
console.log(a);//["qwe","asd","zxc"]
//alert(a.toString);
//alert(a.valueOf());
//alert(a);
console.log(a.join("||"));//qwe||asd||zxc,      
a.length=5;
console.log(a.join("||"));//qwe||asd||zxc||||
console.log(a.toString());//qwe,asd,zxc,,

var a=[];
var length=a.push("wer","sdf");//    
console.log(length);//  
console.log(a);//
length=a.push("w");//   
console.log(length);//  
console.log(a);//
var item=a.pop();//      
console.log(item);//     
console.log(a);//
item=a.pop();//   
console.log(item);//     
console.log(a);//

a=["z","x","c"];
item=a.shift();//     
console.log(item);//
console.log(a);//
length=a.unshift("as");//        
console.log(length);//
console.log(a);//

a=[1,2,3,4,5];
console.log(a.reverse());//  ，   
a=[1,2,3,4,10,5];
console.log(a.reverse());//5,10,4,3,2,1  ，   
console.log(a.sort());//1,10,2,3,4,5           ，sort             ，10    2 
//sort         ，   java   
function compare(a,b){
    if(ab)return -1;
    else return 0;
}
console.log(a.sort(compare));//10,5,4,3,2,1                

a=[1,2];
console.log(a.concat(5,6,[3,4]));//[1,2,5,6,3,4]
a=[1,2,3,4,5,6];
console.log(a.slice(3));//[4,5,6]          
console.log(a.slice(3,5));//[3,4]       
console.log(a.slice(5,3));//[]    
console.log(a.slice(7));//[]         

a=[1,2,3,4,5,6,7];
aa=a.splice(1,2);//     ，    
console.log(a);//[1,4,5,6,7]     a
console.log(aa);//[2,3]      

a=[1,2,3,4,5,6,7];
aa=a.splice(1,0,"7","8","9");//               ，         
console.log(a);//[1,"7","8","9",2,3,4,5,6,7]     a
console.log(aa);//[] 

a=[1,2,3,4,5,6,7];
aa=a.splice(1,1,"7","8","9");//               ，         
console.log(a);//[1,"7","8","9",3,4,5,6,7]     a，   2   
console.log(aa);//2   ，       

a=[1,2,3,4,5,4,3,2,1];
console.log(a.indexOf(2));//1        
console.log(a.indexOf(2,3));//7         2，     
console.log(a.lastIndexOf(2));//7         ，     
console.log(a.lastIndexOf(2,3));//1   
console.log(a.lastIndexOf(9));//-1        1
console.log(a.lastIndexOf("2"));//-1              ===

if (!Array.prototype.indexOf){  //                
        Array.prototype.indexOf = function(elt /*, from*/){  
        var len = this.length >>> 0;  
        var from = Number(arguments[1]) || 0;  
        from = (from < 0)  
             ? Math.ceil(from)  
             : Math.floor(from);  
        if (from < 0)  
          from += len;  
        for (; from < len; from++)  
        {  
          if (from in this &&  
              this[from] === elt)  
            return from;  
        }  
        return -1;  
      };  
    }

a=[1,2,3,4,5];
aa=a.every(function(item,index,array){
    console.log(item);//     
    console.log(index);//     
    console.log(array);//    
    return item>=1;//      1   true
})
console.log(aa);//true
aa=a.every(function(item,index,array){
    console.log(item);//     
    console.log(index);//     
    console.log(array);//    
    return item>2;//       2，         
})
console.log(aa);//false

a=[1,2,3,4,5];
aa=a.some(function(item,index,array){
    return item>4;//        true
})
console.log(aa);//true
aa=a.every(function(item,index,array){
    return item>6;//     
})
console.log(aa);//false

a=[1,2,3,4,5];
aa=a.filter(function(item,index,array){
    return item>3;//            
})
console.log(aa);//[4,5]

a=[1,2,3,4,5];
aa=a.map(function(item,index,array){
    return item*3;
})
console.log(aa);//[3,6,9,12,15]
aa=a.map(function(item,index,array){
    return item>3;
})
console.log(aa);//[false,false,false,true,true]

a=[1,2,3,4,5];
a.forEach(function(item,index,array){
    console.log(item);
    console.log(index);
    console.log(array);
})

a=[1,2,3,4,5];
aa=a.reduce(function(pre,cur,index,array){
    console.log(pre+"   "+cur+"   "+index);pre   return        ，cur             
    return pre+cur;
})
console.log(aa);//15            
//   reduceRight  ，