在 TypeScript 数字上检查空字符串和空字符串的最简单方法
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Easiest way to check for null and empty string on a TypeScript number
提问by Josh
I'm surprised this question hasn't been asked, so maybe I'm overlooking the obvious. I have a form field that is supposed to be a number. Its starting value is null, but once a number is entered and cleared, its an empty string. It looks like JavaScript treats "" like 0 for numeric purposes.
我很惊讶这个问题没有被问到，所以也许我忽略了显而易见的问题。我有一个应该是数字的表单域。它的起始值为空，但一旦输入并清除一个数字，它就是一个空字符串。出于数字目的，JavaScript 似乎将 "" 视为 0。
So, instead of saying...
所以，与其说...
if ((this.RetailPrice != null && this.RetailPrice != 0) || this.RetailPrice === 0) {
return this.RetailPrice;
}Is there a way to extend the TypeScript number type to have a IsNullOrEmpty() method? Or something similar that would simplify this expression?
有没有办法将 TypeScript 数字类型扩展为具有 IsNullOrEmpty() 方法？或者类似的东西可以简化这个表达式？
Ultimately, I think I was looking for something as simple as...
最终，我想我正在寻找一些简单的东西......
if (this.RetailPrice) {
}
回答by Parveen Sachdeva
You can simply use typeof. It will check undefined, null, 0 and "" also.
您可以简单地使用 typeof。它也会检查 undefined、null、0 和 ""。
if(typeof RetailPrice!='undefined' && RetailPrice){
return this.RetailPrice;
}
回答by Asanka Siriwardena
To excludes blank strings as well
也排除空字符串
if(this.retailPrice && this.retailPrice.trim()){
//Implement your logic here
}