JavaScript中的内置对象有以下6个:
1.Number对象
2.Boolean对象
3.Data对象
4.Math对象
5.String对象
6.Array对象
在JavaScript中,数字是一种基本的数据类型,同时JavaScript还支持Number这个对象,该对象是原始数值的包装对象。在必要的时候,JavaScript会自动地在原始数据和对象之间转换。
创建一个Number对象的2中不同方法:
var num1=Number("123");
var num2=new Number("456");
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第一:Number对象常用属性
在Number对象属性中NaN是一个很重要的属性。NaN是Not A Number的缩写,中文意思是:非数字。
需要判断一个值是不是数字,使用isNaN()函数,NaN与所有值都不相等,包括它自己。
第二:Number对象常用方法
Number对象常用方法有toString()和toFixed()
toString()方法将一个Number对象转换为一个字符串,NumberObject.toString(radix);radix是一个可选的参数,规定表示数字的基数。
<script type="text/javascript">
var number = new Number(123);
document.write (number.toString());//output:123
</script>
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toFixed()方法可以把Number四舍五入为指定的小数位数的数字
NumberObject.toFixed(num);num为规定小数的位数。
<script type="text/javascript">
var num = new Number(12.48);
document.write (num.toFixed(1));//output:12.5
</script>
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第三:isNaN的使用
<script type="text/javascript">
document.write(isNaN(123)+"<br/>");//output:true
document.write(isNaN("Hello")+"<br/>");//output:false
</script>
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参考地址:
1.http://www.w3school.com.cn/js/jsref_obj_number.asp
2.https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/NaN