<button type="button" onclick=“alert('欢迎!')">点我!</button>

<h1>我的第一段 JavaScript</h1>
<p id="demo">
JavaScript 能改变 HTML 元素的内容。
</p>
<script>
function myFunction(){
    x=document.getElementById("demo");  // 找到元素
    x.innerHTML="Hello JavaScript!";    // 改变内容
}
</script>
<button type="button" onclick="myFunction()">点击这里</button>

window.alert(5 + 6);

document.getElementById(“demo").innerHTML="段落已修改。";

使用 console.log() 方法在浏览器中（调试模式）显示 JavaScript 值

var i;
var cars = new Array();
cars[0] = "Saab";
cars[1] = "Volvo";
cars[2] = "BMW";
for (i=0;i<cars.length;i++){
document.write(cars[i] + "<br>");
}

var cars=new Array(“Saab","Volvo","BMW");

var cars=["Saab","Volvo","BMW"];

var person={firstname:"John", lastname:"Doe", id:5566};

name=person.lastname;
name=person[“lastname"];

var carname = new String;
var x = new Number;
var y = new Boolean;
var cars = new Array;
var person = new Object;