SOURCE

function writeDocument(variable) {
    document.write(variable + "<br/>");
} 
writeDocument("数组创建------------------------------------");
var arr=["HTML","CSS","JavaScript","jQuery","Vue.js" ];
writeDocument(arr);

writeDocument("数组小标取值------------------------------------");
writeDocument(arr[2]);

writeDocument("数组赋值------------------------------------");
arr[4]="React.js";
writeDocument(arr);

arr[5]="Vue.js";
writeDocument(arr);

arr[8]="Angular.js";
writeDocument(arr);

//2022/3/21

writeDocument("获取数组长度------------------------------------");
writeDocument("数组的长度为：" + arr.length);

writeDocument("获取数组的1-2号元素------------------------------------");
writeDocument(arr.slice(1,3));

writeDocument("往数组头添加元素----------------------------");
arr.unshift("xx");
writeDocument(arr);

writeDocument("往数组尾部添加元素----------------------------");
arr.push("yy");
writeDocument(arr + "<br/>");

writeDocument("删除数组的第一个元素----------------------------");
arr.shift();
writeDocument(arr + "<br/>");

writeDocument("删除数组的最后一个元素----------------------------");
arr.pop()
writeDocument(arr); 

writeDocument("对字符串数组进行升序的排序----------------------------");
writeDocument(arr.sort());

var numArr=[3,4,11,12,9,10];

function upCompare(left,right){
    if(left - right > 0){
        return 1;
    }
    if(left - right == 0){
        return 0;
    }
    if(left - right < 0){
        return -1;
    }
}

function downCompare(left,right){
    if(left - right > 0){
        return -1;
    }
    if(left - right == 0){
        return 0;
    }
    if(left - right < 0){
        return 1;
    }
}

writeDocument("打印排序前的数字数组：" + numArr);
writeDocument("打印升序排列后的数字数组：" + numArr.sort(upCompare));
writeDocument("打印降序排列后的数字数组：" + numArr.sort(downCompare));

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

writeDocument("给字符添加尖括号----------------------------");
function addAngleBracket(strValue){
    var a = strValue.split("").join("><");
    var b = a.split("");//切开
    b.unshift("<");
    b.push(">");
    return b.join("");//连接
}
var strValue = "绿叶学习网";
writeDocument(strValue);
writeDocument(addAngleBracket(strValue));