Add LastArrayElement, Split, and Trim types

[kainiedziela]

Fixes #148

Split

Represents an array of strings split using a passed-in character or character set.

Use case: defining the return type of the String.prototype.split method.

declare function split<S extends string, D extends string>(string: S, separator: D): Split<S, D>;

type Item = 'foo' | 'bar' | 'baz' | 'waldo';
const items = 'foo,bar,baz,waldo';
let array: Item[];

array = split(items, ',');

TakeLast

Extracts the type of the last element of an array.

Use case: Defining the return type of functions that extract the last element of an array, for example lodash.last.

declare function lastOf<V extends any[], L extends TakeLast<V>>(array: V): L;
const array = ['foo', 2];
typeof lastOf(array); // -> number;

Trim

Removes spaces from the edges of a string.

Trim<' foo '> // => 'foo';

[sindresorhus]

I struggle to see where I would use TakeLast in real-world code though? lodash.last would already ship the type itself, so not the best argument. Any other use-cases?

[sindresorhus]

// @mmkal In case you would be willing to help review.

[mmkal]

I can see valid userland use cases for LastArrayElement, maybe getting the last argument from a function? e.g. type MyFuncOptions = LastArrayElement<Parameters<typeof myFunc>>

[mmkal]

Sorry to keep submitting separate reviews! Won't have much chance to look today after this.

[fregante]

I don’t think QuerySelector needs to be part of type-fest. The original author of those types already published and improved on them: https://github.com/g-plane/typed-query-selector

[sindresorhus]

I agree with @fregante. That package does it better than what we're doing here.

I still think the other types added here are useful though.

@kainiedziela Would you be able to remove the QueryResult type, but keep the others? And also link to https://github.com/g-plane/typed-query-selector in a Related section in the readme.

[kainiedziela]

There you go!