SOURCE

function writeDocument(variable) {
    document.write(variable + "<br/>");
} 


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("数组的长度为"+arr.length);
writeDocument("数组1-2号元素是"+arr.slice(1,3));
writeDocument(arr.unshift("aeb","Technology"));
writeDocument(arr);
writeDocument(arr.push("Bootstrop","Sass"));
writeDocument(arr);
writeDocument("删除元素"+arr.shift());
writeDocument(arr);
writeDocument("删除元素"+arr.pop());
writeDocument(arr);
writeDocument(arr.sort());

var numArr=[3,6,9,1,4,13];
writeDocument("排序前"+numArr);
function upcompare(a,b){
    if(a>b){
        return 1;
    }
    if(a==b){
        return 0;
    }
    if(a<b){
        return -1;
    }
}
numArr.sort(upcompare);
writeDocument("升序排序后"+numArr);

function downcompare(a,b){
    if(a>b){
        return -1;
    }
    if(a==b){
        return 0;
    }
    if(a<b){
        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(""+numArr.join("><"));

function add(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(add("绿叶学习网"));