1 //第一种是使用Array构造函数
2 var colors = new Array();
3 var colors = new Array(20);  //创建length为20的数组
4 var colors = new Array("red","blue","green");
5 //第二种基本方式是使用数组字面量表示法
6 var colors = ["red","blue","green"];

1 var colors = ["red","blue","green"];
2 console.log(colors.length);   //3

1 var colors = ["red","blue","green"];
2 var isArray = Array.isArray(colors);
3 console.log(isArray);        //ture 

1 var colors = ["red","blue","green"];
2 console.log( colors );  //red,blue,green
3 console.log( colors.toString );     //red,blue,green
4 console.log( colors.valueOf() );   //red,blue,green
5 console.log( colors.join("&") );    //red&blue&green

1 var colors = ["red","blue","green"];
2 colors.push("black");
3 alert( colors );  //  red,blue,green,black
4 var item = colors.pop();
5 alert( item );   //black
6 alert( colors.length );  //3

 1 var colors = ["red","blue","green"];
 2 var item = colors.shift();  //取地第一项
 3 alert( item );  //red
 4 alert( colors );   //blue,green
 5
 6 var count = colors.unshift(“red”,"black");  //推入两项
 7 alert( colors );   //red,black,blue,green
 8
 9 var item = colors.pop();  //取得最后一项
10 alert( item );  //green
11 alert( colors );  //red,black,blue

 1 var values = [0,1,5,10,15];
 2 values.reverse();    //反转数组项的顺序
 3 alert(values);   //15,10,5,1,0
 4
 5 values.sort();
 6 //sort()方法会调用每个数组项的 toString() 转型方法，然后比较得到的字符串
 7 alert(values);  //0,1,10,15,5
 8
 9 //降序排序
10 function compare(value1,value2){
11   if(value1 < value2){
12       return 1;
13   } else if (value1 > value2){
14       return -1;
15   }else{
16      return 0;
17   }
18 }
19 var values = [0, 1, 5, 10, 15];
20 values.sort(compare);
21 alert(values);  //15,10,5,1,0
22
23 //更简单的比较函数
24 function compare(values1, values2){
25   return value1 - value2;
26 }

1 var colors = ["red","blue","green"];
2 var colors2 = colors.concat("yellow", ["black", "brown"]);
3 alert( colors2 );  //red,blue,green,yellow,black

 1 var colors = ["red","blue","green","yellow","black"];
 2 var colors2 = colors.slice(1);
 3 var colors3 = colors.slice(1, 4);
 4 alert(colors2);  //blue,green,yellow,black
 5 alert(colors3);  //blue,green,yellow
 6
 7
 8 var colors4 = colors.slice(-2, -1);
 9 var colors5 = colors.slice(3, 4);
10 alert(colors4);  //yellow
11 alert(colors5);  //yellow

1 var numbers = [1,2,3,4,5,4,3,2,1];
2 alert(number.indexOf(4));  //3
3 alert(number.lastIndexOf(4));  //5
4
5 alert(number.indexOf(4, 4));  //5
6 alert(number.lastIndexOf(4, 4)); //3

//没有找到的情况下返回 -1

 1 var number = [1, 2, 3, 4, 5, 4, 3, 2, 1];
 2
 3 var everyResult = numbers.every(function(item, index, array){
 4    return(item > 2);
 5 })
 6 alert(everyResult);   //false
 7
 8 var someResult = numbers.some(function(item, index, array){
 9    return(item > 2);
10 })
11 alert(someResult);   //true
12
13 var filterResult = numbers.filter(function(item, index, array){
14    return(item > 2);
15 })
16 alert(filterResult);   //[3, 4, 5, 4, 3]
17
18 var mapResult = numbers.map(function(item, index, array){
19    return item * 2 ;
20 })
21 alert(mapResult);   //[2, 4, 6, 8, 10, 8, 6, 4, 2]
22
23 var i = 0;
24 numbers.forEach(function(item, index, array){
25     i++;
26 })
27 alert(i);   //9

 1 var values = [1, 2, 3, 4, 5]
 2 var sum = values.reduce(function(prev, cur, index, array){
 3     return prev + cur;
 4 });
 5 alert(sum)  //15//第一次执行回调函数，prev是1，cur是2。第二次，prev是3（1加2的结果），cur是3（数组的第三项）。
 6
 7 var sum = values.reduceRight(function(prev, cur, index, array){
 8     return prev + cur;
 9 });
10 alert(sum)  //15

//第一次执行回调函数，prev是5，cur是4。第二次，prev是9（5加4的结果），cur是3（数组的倒数第三项）。