数组方法

<script type="text/javascript">
    var arr1 = [1,2,3,4];
    console.log(arr1.slice(1,3));
    console.log(arr1.join(""))//1234  
    console.log(arr1.join("a"));//1a2a3a4  join()转为字符串
    arr1.unshift("a");//unshift()往数组的前面添加元素
    console.log(arr1);//["a", 1, 2, 3, 4]
    arr1.shift("a");//shift()删除数组最前面的元素
    console.log(arr1);//[1, 2, 3, 4]
    arr1.push("b");//push()往数组的后面添加元素
    console.log(arr1);//[1, 2, 3, 4, "b"]
    arr1.pop();//pop()删除数组最后一位
    console.log(arr1);//[1, 2, 3, 4]

    //splice() 3个参数，第一个参数是指下标，第二项是指删除几位，0就是不删除，
    //第三个参数指要添加的元素 
    var arr2 = [1,2,3,4]
    arr2.splice(0,2,"s");
    console.log(arr2);
    var arr3 = [1,2,3,4]
    console.log(arr3.indexOf(1));//0
    console.log(arr3.reverse());//[4, 3, 2, 1] 倒序

    //**字符串倒叙
    var str = "abccd";
    var str1 = str.split("").reverse().join("");
    console.log(str1);//dccba

</script>