SOURCE

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

writeDocument("数组下标取值-----------------------")
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);

function getNum(str) {
            var num = 0;
            for (var i = 0; i < str.length; i++) {
                var char = str.charAt(i);
                if (char != " " && !isNaN(char)) {
                    num++;
                }
            }
            return num;
        }
        document.write(getNum("166673988zgfyv663"));



        
writeDocument("获取数组的长度----------------------------");
var arr=["ab","cd","ef"]
writeDocument(length);

writeDocument("获取数组的1-2号元素----------------------------");

writeDocument("往数组头添加元素----------------------------");
writeDocument("往数组尾部添加元素----------------------------");
writeDocument("删除数组的第一个元素----------------------------");
writeDocument("删除数组的最后一个元素----------------------------");