String.prototype.matchAll must return RegExpExecArray

[nihil-admirari]

⚙ Compilation target

ESNext

⚙ Library

ESNext

Missing / Incorrect Definition

es2020.string.d.ts defines matchAll as returning RegExpMatchArray:

interface String {
    matchAll(regexp: RegExp): IterableIterator<RegExpMatchArray>;
}

RegExpMatchArray has optional index and input:

interface RegExpMatchArray extends Array<string> {
    index?: number;
    input?: string;
    0: string;
}

MDN says that matchAll returns an iterator of matches:

Each match is an array with the same shape as the return value of RegExp.prototype.exec().

But RegExpExecArray's index and input are not optional:

interface RegExpExecArray extends Array<string> {
    index: number;
    input: string;
    0: string;
}

Sample Code

Array.from(str.matchAll(separator)).forEach(m => {
    // doesn't compile with `strictNullChecks`, since `m.index` is `number | undefined`
    const lastIdx = m.index + m[0].length;
});

Documentation Link

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/matchAll#return_value

[jakebailey]

#36788 ?

[nihil-admirari]

Oops. Closing as a duplicate.