Typescript assign a variable of multi type containing OR ( | ) to single type variable-CodePudding

I have a variable that has type of number or string. How can I assign its value to a variable that accepts number only?

const id:Record<string, string|number> = {name:3}
let num: Record<string, number>;

num = id; //Shows error here

I know there can be javascript work arounds like writing a conversion function, but I am learning Typescript and want to know if there are keywords or typescript specific solutions that are meant to be used in such cases, like as Record<string,string>... that can cast it, instead of type assertion

Here is a link to the code on Typescript playground

CodePudding user response：

It looks like you already answered your question, you can cast with the as keyword.

num = id as number

If you wanted to get fancy you could check the id's type with typeof so something like this

if (typeof id === 'number') {
  number = id
}

CodePudding user response：

Just use Number().

TypeScript provides static type checking, but those types don't have any effect at runtime. Doing something like as asserts to TypeScript about a variable's type, but it will not actually perform a "cast." If you want your string to be parsed into a number, this will not work.