locutus/kotlin/collections/runningFold.js

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

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.runningFold = runningFold;
function runningFold(values, initial, operation) {
    //  discuss at: https://locutus.io/kotlin/collections/runningFold/
    // original by: Kevin van Zonneveld (https://kvz.io)
    //      note 1: Returns successive accumulation values including initial, like Kotlin runningFold.
    //   example 1: runningFold([1, 2, 3, 4], 0, (acc, value) => acc + value)
    //   returns 1: [0, 1, 3, 6, 10]
    //   example 2: runningFold(['a', 'b', 'c'], '', (acc, value) => acc + value)
    //   returns 2: ['', 'a', 'ab', 'abc']
    //   example 3: runningFold([], 10, (acc, value) => acc + value)
    //   returns 3: [10]
    if (typeof operation !== 'function') {
        throw new TypeError('runningFold(): operation must be a function');
    }
    if (!Array.isArray(values)) {
        return [initial];
    }
    const array = values;
    const out = [initial];
    let accumulator = initial;
    for (let i = 0; i < array.length; i++) {
        accumulator = operation(accumulator, array[i], i, array);
        out.push(accumulator);
    }
    return out;
}