<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>JavaScript中有5种数据类型</title>
<!--
1.String
2.Number
3.Object
4.function
5.boolean
3中对象类型
1.Object
2.Date
3.Array
2个不包含任何值的数据类型
1.null 2.undefined
-->
</head>
<body>
<p>typeof 操作返回变量、对象、函数、表达式类型</p>
<p id="demo"</p>
<script>
document.getElementById("demo").innerHTML =
typeof "john" + "<br>" +
typeof 3.14 + "<br>" +
typeof NaN + "<br>" +
typeof false + "<br>" +
typeof [1,2,3,4] + "<br>" +
typeof {name:"john",age:34} + "<br>" +
typeof new Date() + "<br>" +
typeof function (){} + "<br>" +
typeof myCar + "<br>" +
typeof null +
false.constructor + "<br>" +
new Date().constructor + "<br>" +
[1,2,3,4].constructor + "<br>" +
function(){}.constructor;
</script>
<p>判断是否为数组</p>
<p id="demo1"></p>
<script>
var fruits = ["banana","orange","apple","mango"];
document.getElementById("demo1").innerHTML = isArray(fruits);
function isArray(myArray){
return myArray.constructor.toString().indexOf("Array") > -1;
}
</script>
<p>toSting()方法将数字转换为字符串</p>
<p id="demo2"></p>
<script>
var x = 123;
document.getElementById("demo2").innerHTML =
x.toString() + "<br>" +
(123).toString() + "<br>" +
(100 + 23).toString();
</script>
</body>
</html>
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