typescript 打字稿：检查字符串中的数字
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Typescript : check a string for number
提问by Rahul Misra
I'm new to web development, and in my function want to check if a given string value is a number. In case the string isn't a valid number I want to return null.
我是 Web 开发的新手，在我的函数中想检查给定的字符串值是否为数字。如果字符串不是有效数字，我想返回 null。
The following works for all cases except when the string is "0" in which case it returns null.
以下适用于所有情况，除非字符串为“0”，在这种情况下它返回 null。
parseInt(columnSortSettings[0]) || null;
How do I prevent this from happening. Apparantly parseInt doesn't consider 0 as an integer!
我如何防止这种情况发生。显然 parseInt 不认为 0 作为整数！
回答by Pranav C Balan
回答by Eric
It's because you are basically testing 0 which is also false. You can do
这是因为您基本上是在测试 0，这也是错误的。你可以做
var n = columnSortSettings[0];
if(parseInt(n, 10) || n === '0'){
//...
}
You can also test instead if it's a number
你也可以测试它是否是一个数字
if(typeof(parseInt(n, 10)) === 'number'){
//...
}
But beware cause
但要注意原因
typeof Infinity === 'number';
typeof NaN === 'number';
回答by Richard Lee
You can use the isNumericoperator from rxjslibrary (importing rxjs/util/isNumeric
您可以使用ISNUMERIC从运营商rxjs库（进口rxjs / UTIL / ISNUMERIC
