字符串插值
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript 模板字面量</h2>
<p>模板字面量允许字符串中的变量：</p>
<p id="demo"></p>
<p>Internet Explorer 不支持模板字面量。</p>
<script>
var firstName = "John";
var lastName = "Doe";
var text = `Welcome ${firstName}, ${lastName}!`;
document.getElementById("demo").innerHTML = text;
</script>
</body>
</html>
模板字面量
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript 模板字面量</h2>
<p>模板字面量允许字符串中的变量：</p>
<p id="demo"></p>
<p>Internet Explorer 不支持模板字面量。</p>
<script>
let header = "Templates Literals";
let tags = ["template literals", "javascript", "es6"];
let html = `<h2>${header}</h2><ul>`;
for (const x of tags) {
html += `<li>${x}</li>`;
}
html += `</ul>`;
document.getElementById("demo").innerHTML = html;
</script>
</body>
</html>
确定是否是数
<!DOCTYPE html>
<html>
<body>
<h1>JavaScript 数字</h1>
<p>您可使用全局 JavaScript 函数 isNaN() 来确定某个值是否是数：</p>
<p id="demo"></p>
<script>
var x = 100 / "Apple";
document.getElementById("demo").innerHTML = isNaN(x);
</script>
</body>
</html>
超出数字范围
<!DOCTYPE html>
<html>
<body>
<h1>JavaScript 数字</h1>
<p>Infinity （或 -Infinity）是 JavaScript 在计算数时超出最大可能数范围时返回的值：</p>
<p id="demo"></p>
<script>
var myNumber = 2;
var txt = "";
while (myNumber != Infinity) {
myNumber = myNumber * myNumber;
txt = txt + myNumber + "<br>";
}
document.getElementById("demo").innerHTML = txt;
</script>
</body>
</html>
请不要创建数值对象。这样会拖慢执行速度。
new关键词使代码复杂化，并产生某些无法预料的结果