JS 数组方法 实例

   /* 数组转为字符串，用join(" ")方法,原数组不变，返回新字符串 */
        var arr = new Array;
        arr[0] = "hello";
        arr[1] = "melin";
        var str =arr.join(" ");
        console.log(arr);       //［“hello”,"melin"］
        console.log(arr.length);//2
        console.log(str);       //hello melin
        console.log(str.length);//11

    /* 字符转为数组，用split(" ")方法,原字符串不变，返回新数组 */
        var str = "hello melin go!";
        var arr =[];
        arr = str.split(" ");
        console.log(str);       //hello melin go!
        console.log(str.length);//15
        console.log(arr);       //["hello","melin","go!"]
        console.log(arr.length);//3
        console.log(arr[0]);    //hello
        console.log(arr[1]);    //melin
        console.log(arr[2]);    //go!

    /* 数组，shift方法 ,对原数组删除其第一个元素，返回删除的元素*/
        var arr1 = [5,6,7,8];
        var p;
        p = arr1.shift();
        console.log(arr1); //[6,7,8]
        console.log(p);    //5

    /* 数组，pop方法 ,对原数组删除其最后一个元素，返回删除的元素*/        
        var arr1 = [5,6,7,8];
        var p ;
        p = arr1.pop();
        console.log(arr1);  //[5,6,7]
        console.log(p);     //8
        
    /* 数组，push方法 ,对原数组追加最后一个元素，返回数组长度 */ 
        var arr1 = [5,6,7,8];
        var c = 9,p;
        p = arr1.push(c);
        console.log(arr1); //[5,6,7,8,9]
        console.log(p);    //5

    /* 数组，unshift方法 ,对原数组增加第一个元素，返回数组长度*/ 
        var arr1 = [5,6,7,8];
        var c = 4,p;
        p = arr1.unshift(c);
        console.log(arr1); //[4，5,6,7,8]
        console.log(p);    //5

    /* 数组，splice(start,num,arr1,arr2...)方法 ,对原数组删除从start开始num个原数组
    ，返回删除的数组 */ 
        var arr1 = [5,6,7,8];
        var arr2;
        var arr3 = [9,10];
        arr2 = arr1.splice(1,2,arr3,4);
        console.log(arr1);    //[5,[9,10],4,8]
        console.log(arr2);    //[6,7]   

    /* 数组，slice(start,end)方法 ,对原数组删除从start开始到end结束
    ，返回删除的数组 */ 
        var arr1 = [4,5,6,7];
        var arr2,arr3,arr4,p;
        arr2 = arr1.slice(2,3);
        arr3 = arr1.slice(2);
        arr4 = arr1.slice(-3,-2);
        console.log(arr1); //[4,5,6,7]
        console.log(arr2); //[6]
        console.log(arr3); //[6,7]
        console.log(arr4); //[5]

    /* 数组，concat方法 ,连接两数组，返回新数组*/ 
        var arr1 = [4,5,6,7],arr2 = [8,9];
        var arr3,arr4;
        arr3 = arr1.concat(arr2);
        arr4 = arr2.concat(arr1);
        console.log(arr1); //[4,5,6,7]
        console.log(arr2); //[8,9]
        console.log(arr3); //[4,5,6,7,8,9]
        console.log(arr4); //[8,9,4,5,6,7]

    /* 数组，reverse方法 ,反转原数组，返回新数组*/ 
        var arr1 = [4,5,6,7];
        var arr2;
        arr2 = arr1.reverse();
        console.log(arr1); //[7,6,5,4]
        console.log(arr2); //[7,6,5,4]