console 命令行工具 X clear
console
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);