bbo/es/extend.js

bbo is a utility library of zero dependencies for javascript.

import isObject from './is_object.js';
import './get_tag.js';
import isArray from './is_array.js';
import isFunction from './is_function.js';
import isBoolean from './is_boolean.js';

function extend()
/* [deep], obj1, obj2, [objn] */
{
  var args = [].slice.call(arguments);
  var deep = false;

  if (isBoolean(args[0])) {
    deep = args.shift();
  }

  var result = args[0];

  if (isUnextendable(result)) {
    throw new Error('extendee must be an object');
  }

  var extenders = args.slice(1);
  var len = extenders.length;

  for (var i = 0; i < len; i++) {
    var extender = extenders[i];

    for (var key in extender) {
      if (extender.hasOwnProperty(key)) {
        var value = extender[key];

        if (deep && isCloneable(value)) {
          var base = isArray(value) ? [] : {};
          result[key] = extend(true, result.hasOwnProperty(key) && !isUnextendable(result[key]) ? result[key] : base, value);
        } else {
          result[key] = value;
        }
      }
    }
  }

  return result;
}

function isCloneable(obj) {
  return isArray(obj) || isObject(obj);
}

function isUnextendable(val) {
  return !val || !isObject(val) && !isFunction(val);
}

export default extend;