打字稿类型'数字'不可分配│键入'字符串' [英] Typescript Type 'number' is not assignable │ to type 'string'
问题描述
我目前正在为Angular 4应用制定货币格式指令.在解析后,除去数字和小数点以外的所有内容,最后得到一个字符串化的浮点数,但是我需要它以浮点数形式返回,以便我可以对其进行数学运算.
I am currently knee deep in making a currency formatter directive for an Angular 4 app. on the parse strip out everything other than the numbers and the decimal and end up with a stringified float, but I need it to return as a float so I can do math with it.
parse(value: string, fractionSize: number = 2): number {
let val = value.replace(/([^0-9.])+/ig, '');
let [ integer, fraction = "" ] = (val || "").split(this.DECIMAL_SEPARATOR);
integer = integer.replace(new RegExp(this.THOUSANDS_SEPARATOR, "g"), "");
fraction = parseInt(fraction, 10) > 0 && fractionSize > 0
? this.DECIMAL_SEPARATOR + (fraction + PADDING).substring(0, fractionSize)
: "";
let result = `${integer}${fraction}`;
// at this point result = "100.55";
result = parseFloat(result); // this refuses to compile saying "Type 'number' is not assignable │ to type 'string'"
return result;
}
推荐答案
两行:
let result = `${integer}${fraction}`;
result = parseFloat(result);
是问题所在.当未明确声明变量时,Typescript可以很好地推断出变量的类型.在这种情况下,由于您将字符串分配给 result
,因此typescript推断其类型为字符串.要解决此问题,您有两个选择.首先,显式声明该变量的类型,以便它允许包含字符串和数字:
are the problem. Typescript is pretty good about infering the type of a variable when it's not explicitly declared. In this case, because you assign a string to the result
, typescript infers it's type as a string. To fix this, you have two options. First, explicitly declare the type of that variable so that it allows both strings and numbers:
let result: string|number = `${integer}${fraction}`;
result = parseFloat(result); // now should be ok.
或者您可以将解析后的数字分配给新变量,而不是重新使用 result
变量:
Or you can assign the parsed number to a new variable, instead of reusing the result
variable:
let result = `${integer}${fraction}`;
let numberResult = parseFloat(result); // now should be ok.
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