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    <title>Document</title>
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    <script>
        var date = new Date();
        var arr = new Array();
        var obj = new Object();
        var x = new Number();
        var y = new String();
        var z = new Boolean();
        console.log(x,y,z);

        //1.Number.isFinite() 判断一个数是否是有限数
        console.log(Number.isFinite(100)); // true
        console.log(Number.isFinite(100 / 0)); //false
        console.log(Number.isFinite(Infinity)); // false
        console.log(Number.isFinite(-Infinity)); //false

        //2.Number.isNaN() 判断是不是非法数字
        console.log(Number.isNaN(123)); // false

        // 3.Number.parseInt() 将字符串转换为整数
         console.log(Number.parseInt("3.14"));

        // 4.Number.parseFloat() 将字符串转换为浮点数
         console.log(Number.parseFloat("3.14"));

        // 5.Number.isInteger() 判断当前值是否是整数
        console.log(Number.isInteger(5.4));
        console.log(Number.isInteger(5));

        // 6.Math.trunc() 抹平小数 返回整数
        console.log(Math.trunc(6.3));

        // 7.Math.sign() 传入的值 是正数，负数还是0
        console.log(Math.sign(199)); //1
        console.log(Math.sign(-199)); //-1
        console.log(Math.sign(0));//0

    </script>
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