locutus/esm/python/_helpers/_functools.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

export const noInitializer = Symbol('noInitializer');
export function pythonReduce(func, iterable, initializer = noInitializer) {
    const iterator = toIterator(iterable, 'reduce');
    let accumulator;
    if (initializer !== noInitializer) {
        accumulator = initializer;
    }
    else {
        const first = iterator.next();
        if (first.done) {
            throw new TypeError('reduce() of empty sequence with no initial value');
        }
        accumulator = first.value;
    }
    while (true) {
        const next = iterator.next();
        if (next.done) {
            return accumulator;
        }
        accumulator = func(accumulator, next.value);
    }
}
function toIterator(iterable, functionName) {
    if (typeof iterable === 'string') {
        return iterable[Symbol.iterator]();
    }
    if ((typeof iterable === 'object' || typeof iterable === 'function') && iterable !== null) {
        const iterableValue = iterable;
        const iteratorFactory = iterableValue[Symbol.iterator];
        if (typeof iteratorFactory === 'function') {
            return iteratorFactory.call(iterableValue);
        }
    }
    throw new TypeError(`${functionName}() expected an iterable`);
}