Tricks I wish I knew when I learned TypeScript
1–10 of 276 posts
Re: Tricks I wish I knew when I learned TypeScript
#2Note: don't use typeof x === 'object' to check whether something is a valid object, because it will return true for arrays as well.
Arrays are objects, so this is expected behaviour.
Re: Tricks I wish I knew when I learned TypeScript
#3The third example describes something useful in record types, but goes about it in what seems an odd way, and ends up suboptimal as a result. I'd instead use an object type like this:
type Human = {
name: string;
age: number;
}
Re: Tricks I wish I knew when I learned TypeScript
#4 interface Person {
[key: AllowedKeys]: unknown
}
type Person = {
[key in AllowedKeys]: unknown
};
Re: Tricks I wish I knew when I learned TypeScript
#5Note: don't use typeof x === 'object' to check whether something is a valid object, because it will return true for arrays as well. Arrays are objects, so this is expected behaviour.
And it will return true for null as well ;)
Re: Tricks I wish I knew when I learned TypeScript
#6Note that `Readonly` does not prevent a call to side-effect methods when `T` is not among a predefined set of built-in types. Indeed, it prevents such calls only on predefined types such as arrays, maps, and sets. It could be more "accurate" to use `readonly number[]` instead of `Readonly>` for highlighting the difference.
Re: Tricks I wish I knew when I learned TypeScript
#7Note: don't use typeof x === 'object' to check whether something is a valid object, because it will return true for arrays as well. Arrays are objects, so this is expected behaviour.
Note: please post a better solution.
Re: Tricks I wish I knew when I learned TypeScript
#8Here's another. Instead of returning Sometype|undefined from a function which may or may not have a value to return (such as searchCustomer), return Sometype|null.
That forces the function to return a value that's explicitly intended rather than defaulting from a missed out if-else codepath. This is useful since JS is often imperative style code.
Re: Tricks I wish I knew when I learned TypeScript
#9I actually don't really like Record types in the way people/library maintainers often use them - the type-checker asserts that values are actually present for all the specified keys, which is fine if the objects with the Record type really were exhaustive; but instead I often see them used where the reality of the data is a Partial - some keys are missing. Something about the abstraction causes people to misuse it frequently.