var arr = new Array(); 
var arr = []; 

var arr = new Array(3);  //数组长度为3 

var arr = new Array("red","green","blue"); 

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

if(Array.isArray(arr)){ 
    //执行某些操作 
} 

var arr = ["red","green","blue"]; 
console.log(arr.toString());  //red,green,blue 
console.log(arr.valueof());  //red,green,blue 
console.log(arr);       //red,green,blue 

var arr = ["red","green","blue"]; 
console.log(arr.join(","));  //red,green,blue 
console.log(arr.join("||"));  //red||green||blue 

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

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

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

var arr = [1,2,3]; 
arr.unshift(4);  //返回长度4 
arr.unshift(5);  //返回长度5 
console.log(arr);  //[1,2,3,4,5] 

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

function compare(value1,value2){ 
  return value1-value2; 
} 
var arr = [1,3,2,5,4]; 
arr.sort(compare); 
console.log(arr);  //[1,2,3,4,5] 

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

var arr = [1,2,3,4,5]; 
var arr2 = arr.slice(1);  //[2,3,4,5] 
var arr3 = arr.slice(1,3);  //[2,3] 

var arr = [1,2,3,4,5]; 
arr.splice(2,0,11,22);  //从位置2插入两项，没有删除 
console.log(arr);  //[1,2,11,22,3,4,5] 
 
arr.splice(2,2,33,44);  //从位置2开始删除两项，插入两项，返回被删除的项 
console.log(arr);  //[1,2,33,44,4,5] 
 
arr.splice(1,1);  //从位置1开始删除1项，返回被删除的项 
console.log(arr);  //[1,33,44,4,5] 

var arr = [1,2,3,4,5,4,3,2,1]; 
console.log(arr.indexOf(4));  //3 
console.log(arr.lastIndexOf(4));  //5 
 
console.log(arr.indexOf(4,4));  //5 
console.log(arr.lastIndexOf(4,4));  //3 

var arr = [1,2,3,4,5,4,3,2,1]; 
var everyResult = arr.every(function(item,index,array){ 
  return (item>2); 
}); 
console.log(everyResult);  //false，并不是全部大于2 
 
var someResult= arr.some(function(item,index,array){ 
  return (item>2); 
}); 
console.log(someResult);  //true，某一项大于2即可 

var arr = [1,2,3,4,5,4,3,2,1]; 
var filterResult = arr.filter(function(item,index,array){ 
  return (item>2); 
}); 
console.log(filterResult);  //[3,4,5,4,3],返回所有数值都大于2的一个数组 

var arr = [1,2,3,4,5,4,3,2,1]; 
var mapResult = arr.map(function(item,index,array){ 
  return item*2; 
}); 
console.log(mapResult);  //[2,4,6,8,10,8,6,4,2]，原先数组每一项乘以2后返回 

var arr = [1,2,3,4,5,4,3,2,1]; 
arr.forEach(function(item,index,array){ 
  //执行某些操作 
}); 

var arr = [1,2,3,4,5]; 
var sum = arr.reduce(function(pre,cur,index,array){ 
  return pre+cur; 
}); 
console.log(sum);  //15