lovecoding
/
VIP32


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var a = '123';
        console.log(typeof null);
        if(null===undefined) {
            console.log(1)
        }else {
            console.log(2)
        }
        // 0.1+0.2!=0.3
        /**
         * 1.typeof 类型判断
         * 2.instanceof
         * 3.Object.prototype.toString.call()
         * 4.constructor
        */
       var fn1 = function() {
        console.log("这是一个函数");
       }
       console.log(fn1 instanceof Function);
       console.log(Object.prototype.toString.call(true));
       var num = 10;
       console.log(num.constructor);
    </script>
</body>
</html>