Ask Your Question
2

Can TypeScript perform narrowing using the NodeJS 'assert' function?

asked 2023-05-26 07:02:06 +0000

djk gravatar image

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted
2

answered 2023-05-26 07:27:02 +0000

david gravatar image

Yes, TypeScript can perform narrowing using the NodeJS 'assert' function. The 'assert' function in NodeJS throws an error if the given condition is not true. This can be used to narrow down the type of a variable in TypeScript.

For example, consider the following code:

function printLength(str: string | number) {
  assert(typeof str === 'string');
  console.log(str.length);
}

Here, we pass a variable 'str' of type 'string | number' to the function 'printLength'. We use the 'assert' function to check if 'str' is a string. If the condition is true, then TypeScript narrows down the type of 'str' to 'string', which we can safely use to access the 'length' property.

If the 'assert' condition is not true, then an error will be thrown at runtime. Therefore, it is important to use the 'assert' function only when we are sure of the type of the variable.

edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account. This space is reserved only for answers. If you would like to engage in a discussion, please instead post a comment under the question or an answer that you would like to discuss

Add Answer


Question Tools

Stats

Asked: 2023-05-26 07:02:06 +0000

Seen: 26 times

Last updated: May 26 '23