@gamestdio/state-listener/lib/compare.js

Deeply compare JavaScript objects and listen to changes.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
function compare(tree1, tree2) {
    var patches = [];
    generate(tree1, tree2, patches, []);
    return patches;
}
exports.compare = compare;
function concat(arr, value) {
    var newArr = arr.slice();
    newArr.push(value);
    return newArr;
}
function objectKeys(obj) {
    if (Array.isArray(obj)) {
        var keys_1 = new Array(obj.length);
        for (var k = 0; k < keys_1.length; k++) {
            keys_1[k] = "" + k;
        }
        return keys_1;
    }
    if (Object.keys) {
        return Object.keys(obj);
    }
    var keys = [];
    for (var i in obj) {
        if (obj.hasOwnProperty(i)) {
            keys.push(i);
        }
    }
    return keys;
}
;
// Dirty check if obj is different from mirror, generate patches and update mirror
function generate(mirror, obj, patches, path) {
    var newKeys = objectKeys(obj);
    var oldKeys = objectKeys(mirror);
    var deleted = false;
    for (var t = oldKeys.length - 1; t >= 0; t--) {
        var key = oldKeys[t];
        var oldVal = mirror[key];
        if (obj.hasOwnProperty(key) && !(obj[key] === undefined && oldVal !== undefined && Array.isArray(obj) === false)) {
            var newVal = obj[key];
            if (typeof oldVal == "object" && oldVal != null && typeof newVal == "object" && newVal != null) {
                generate(oldVal, newVal, patches, concat(path, key));
            }
            else {
                if (oldVal !== newVal) {
                    patches.push({
                        operation: "replace",
                        path: concat(path, key),
                        value: newVal,
                        previousValue: oldVal
                    });
                }
            }
        }
        else {
            patches.push({ operation: "remove", path: concat(path, key) });
            deleted = true; // property has been deleted
        }
    }
    if (!deleted && newKeys.length == oldKeys.length) {
        return;
    }
    for (var t = newKeys.length - 1; t >= 0; t--) {
        var key = newKeys[t];
        if (!mirror.hasOwnProperty(key) && obj[key] !== undefined) {
            var newVal = obj[key];
            var addPath = concat(path, key);
            // compare deeper additions
            if (typeof newVal == "object" && newVal != null) {
                generate({}, newVal, patches, addPath);
            }
            patches.push({ operation: "add", path: addPath, value: newVal });
        }
    }
}