SOURCE

function writeDocument(variable){
    document.write(variable+"<br/>");
}
//数组的赋值
var arr = ["HTML","CSS","JavaScript","jQuery","Vue.js"]; 
writeDocument(arr[2]);
writeDocument(arr);
arr[4]="React.js";
writeDocument(arr);
arr[5]="Vue.js";
writeDocument(arr);
arr[8]="Angular.js";
writeDocument(arr);

writeDocument("获取数组长度------------------------");
 //创建数组
        var arr1 = [];
        var arr2 = [1, 2, 3,];
        //输出数组长度
        writeDocument(arr1.length );
        writeDocument(arr2.length);
writeDocument("获取数组的某一段------------------------");
  var arr = ["a","b","c","d"+"<br/>"];
        writeDocument(arr.slice(1, 3));
writeDocument("往数组头添加元素------------------------");
var arr = ["a", "b"];
        arr.unshift("c", "d");
        writeDocument(arr);
writeDocument("在数组结尾添加元素------------------------");
var arr = ["a", "b"];
        arr.push("c", "d");
        writeDocument(arr);
writeDocument("删除数组第一个元素------------------------");
var arr = ["a", "b","c", "d"];
        arr.shift();
        writeDocument(arr);
writeDocument("删除数组最后一个元素------------------------");
var arr = ["a", "b","c", "d"];
        arr.pop();
        writeDocument(arr);
writeDocument("对字符串数组按升序排序------------------------");
writeDocument(arr.sort());
var numArr=[3,6,9,1,4,11];
writeDocument("排序前："+numArr);
function upcompare(x,y){
    if(x>y){
        return 1;
    }
    if(x==y){
        return 0;
    }
    if(x<y){
        return -1;
    }
}
numArr.sort(upcompare);
writeDocument("升序排序后："+numArr);
function downcompare(x,y){
    if(x>y){
        return -1;
    }
    if(x==y){
        return 0;
    }
    if(x<y){
        return 1;
    }
}
numArr.sort(downcompare);
writeDocument("降序排序后："+numArr);

writeDocument("反转数组："+numArr.reverse());
writeDocument("默认join数组："+numArr.join());
writeDocument("默认join数组："+numArr.join(":"));
writeDocument("默认join数组："+numArr.join("-"));
writeDocument("默认join数组："+numArr.join("><"));

function addAngleBracket(strValue){
    var strArr=strValue.split("");
    console.log(strArr);
    var str=strArr.join("><");
    console.log(str);
    strArr=str.split("");
    console.log(strArr);
    strArr.unshift("<");
    strArr.push(">");
    console.log(strArr);
    return strArr.join("");
}
writeDocument(addAngleBracket("绿叶学习网"));