JSON digest for comparing parsed json payloads

objectDigest.js

goog.provide('json.digest');

goog.require('goog.array');
goog.require('goog.crypt');
goog.require('goog.crypt.Hash');
goog.require('goog.crypt.Sha1');
goog.require('goog.object');

/**
 * @param {Object} item
 * @param {goog.crypt.Hash=} opt_hash
 * @return {string}
 */
json.digest = function(item, opt_hash) {
  return /** @type {string} */ (json.digest_(item, opt_hash));
};

/**
 * @private
 * @param {Object} item
 * @param {goog.crypt.Hash=} opt_hash
 * @param {boolean=} opt_update_only
 * @return {?string}
 */
json.digest_ = function(item, opt_hash, opt_update_only) {
    var hash = opt_hash instanceof goog.crypt.Hash ? opt_hash : new goog.crypt.Sha1();
    /*
     * Keys need to be ordered to guarantee digest will be the same
     * for every call of the same keys
     */
    var sortedKeys = goog.object.getKeys(item);
    goog.array.sort(sortedKeys);
    goog.array.forEach(sortedKeys, function(key) {
        hash.update(key + ':');
        var val = goog.object.get(item, key);
        if (goog.isArrayLike(val)) {
            json.digest_(goog.array.toObject(val, function(el, i) {
                return i + '' /* keys need to be string type */;
            }, this), hash, true);
        }
        else if (goog.isObject(val)) {
            json.digest_(val, hash, true);
        } else {
            hash.update(val + '' /* poor man's cast for undefined/null etc */);
        }
    });
    if (opt_update_only) {
      return null;
    }
    return goog.crypt.byteArrayToHex(hash.digest());
};