shallow-diff/index.js

compare two objects or arrays and return the diff (add/updated/removed/unchanged)

/**
 * @license shallow-diff https://github.com/cosmosio/shallow-diff
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2014-2015 Olivier Scherrer <pode.fr@gmail.com>
 */
"use strict";

function assert(assertion, error) {
    if (assertion) {
        throw new TypeError("simple-loop: " + error);
    }
}

var loop = require("simple-loop");

/**
 * Make a diff between two objects
 * @param {Array/Object} base the base object
 * @param {Array/Object} compared the object to compare the base with
 * @example:
 *  With objects:
 *
 *  base = {a:1, b:2, c:3, d:4, f:6}
 *  compared = {a:1, b:20, d: 4, e: 5}
 *  will return :
 *  {
 *      unchanged: ["a", "d"],
 *      updated: ["b"],
 *      deleted: ["f"],
 *      added: ["e"]
 *  }
 *
 * It also works with Arrays:
 *
 *  base = [10, 20, 30]
 *  compared = [15, 20]
 *  will return :
 *  {
 *      unchanged: [1],
 *      updated: [0],
 *      deleted: [2],
 *      added: []
 *  }
 *
 * @returns object
 */
module.exports = function shallowDiff(base, compared) {
    assert(typeof base != "object", "the first object to compare with shallowDiff needs to be an object");
    assert(typeof compared != "object", "the second object to compare with shallowDiff needs to be an object");

    var unchanged = [],
        updated = [],
        deleted = [],
        added = [];

    // Loop through the compared object
    loop(compared, function(value, idx) {
        // To get the added items
        if (!(idx in base)) {
            added.push(idx);

        // The updated items
        } else if (value !== base[idx]) {
            updated.push(idx);

        // And the unchanged
        } else if (value === base[idx]) {
            unchanged.push(idx);
        }
    });

    // Loop through the before object
    loop(base, function(value, idx) {
        // To get the deleted items
        if (!(idx in compared)) {
            deleted.push(idx);
        }
    });

    return {
        updated: updated,
        unchanged: unchanged,
        added: added,
        deleted: deleted
    };
};