iteragain/dist/esm/internal/GroupByIterator.js

Javascript Iterable/Iterator/Generator-function utilities.

/** Groups values in the input iterator by some key identifier function or property. */
export class GroupByIterator {
    constructor(iterator, key) {
        this.iterator = iterator;
        this.key = key;
        this.currGroup = [];
        this.done = false;
    }
    [Symbol.iterator]() {
        return this;
    }
    next() {
        if (this.done)
            return { done: true, value: undefined };
        let next;
        if (this.currKey === undefined) {
            next = this.iterator.next();
            if (next.done) {
                this.done = true;
                return { done: true, value: undefined };
            }
            this.currKey = this.getKey(next.value);
            this.currGroup.push(next.value);
        }
        while (!(next = this.iterator.next()).done) {
            this.currGroup.push(next.value);
            const nextKey = this.getKey(next.value);
            if (nextKey !== this.currKey) {
                const value = [
                    this.currKey,
                    this.currGroup.splice(0, this.currGroup.length - 1),
                ];
                this.currKey = nextKey;
                return { done: false, value };
            }
        }
        this.done = true;
        return { done: false, value: [this.currKey, this.currGroup] };
    }
    getKey(value) {
        return typeof this.key === 'function' ? this.key(value) : value[this.key];
    }
}
export default GroupByIterator;
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