functional-pollyfills

functional-pollyfills.carbide.md

functional-pollyfills

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test.js

import { map, reduce } from './utils.js' ///import all dependencies

const input = [1, 2, 3, 4, 5] ///set up input data

let a = map(input, i => i + i) ///test map function
let b = map(input, i => i * i)

let c = reduce(input, (m, i) => m + i) ///test reduce function
let d = reduce(input, (m, i) => m * i)

utils.js

export function reduce(arr, callback /*, initialValue*/ ) { ///adapted from:\\https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global\_Objects/Array/Reduce
    'use strict';
    if (arr === null) {
        throw new TypeError('Array.prototype.reduce called on null or undefined');
    }
    if (typeof callback !== 'function') {
        throw new TypeError(callback + ' is not a function');
    }
    var t = Object(arr),
        len = t.length >>> 0,
        k = 0,
        value;
    if (arguments.length == 3) {
        value = arguments[2];
    } else {
        while (k < len && !(k in t)) {
            k++;
        }
        if (k >= len) {
            throw new TypeError('Reduce of empty array with no initial value');
        }
        value = t[k++];
    }
    for (; k < len; k++) {
        if (k in t) {
            value = callback(value, t[k], k, t);
        }
    }
    return value;
}

export function map(arr, callback, thisArg) { ///adapted from:\\https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global\_Objects/Array/Map

    var T, A, k;

    if (arr == null) {
        throw new TypeError(' this is null or not defined');
    }

    var O = Object(arr);

    var len = O.length >>> 0;

    if (typeof callback !== 'function') {
        throw new TypeError(callback + ' is not a function');
    }

    if (arguments.length > 1) {
        T = thisArg;
    }

    A = new Array(len);

    k = 0;

    while (k < len) {

        var kValue, mappedValue;

        if (k in O) {

            kValue = O[k];

            mappedValue = callback.call(T, kValue, k, O);

            A[k] = mappedValue;

        }

        k++;
    }

    return A;
};