locutus/clojure/core/assoc_in.js

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

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.assoc_in = assoc_in;
function cloneForKey(value, nextKey) {
    if (Array.isArray(value)) {
        return value.slice();
    }
    if (typeof value === 'object' && value !== null) {
        return { ...value };
    }
    return typeof nextKey === 'number' ? [] : {};
}
function assoc_in(value, keys, newValue) {
    //      discuss at: https://locutus.io/clojure/assoc_in/
    // parity verified: Clojure 1.12
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Immutably associates a value at a nested path, similar to Clojure assoc-in.
    //       example 1: assoc_in({a: {b: 1}}, ['a', 'b'], 2)
    //       returns 1: {a: {b: 2}}
    //       example 2: assoc_in({a: {}}, ['a', 'c'], 10)
    //       returns 2: {a: {c: 10}}
    //       example 3: assoc_in([1, {x: 3}], [1, 'x'], 9)
    //       returns 3: [1, {x: 9}]
    if (!Array.isArray(keys)) {
        return value;
    }
    if (keys.length === 0) {
        return newValue;
    }
    const root = cloneForKey(value, keys[0]);
    let sourceCursor = value;
    let targetCursor = root;
    for (let i = 0; i < keys.length - 1; i++) {
        const key = keys[i];
        const nextKey = keys[i + 1];
        if (key === undefined || nextKey === undefined) {
            continue;
        }
        const sourceNext = sourceCursor !== null && typeof sourceCursor === 'object'
            ? sourceCursor[key]
            : undefined;
        const clonedNext = cloneForKey(sourceNext, nextKey);
        targetCursor[key] = clonedNext;
        sourceCursor = sourceNext;
        targetCursor = clonedNext;
    }
    const leafKey = keys[keys.length - 1];
    if (leafKey === undefined) {
        return root;
    }
    ;
    targetCursor[leafKey] = newValue;
    return root;
}