lodash/partial.js

define(['./internal/createWrapper', './internal/replaceHolders', './rest'], function(createWrapper, replaceHolders, rest) {

  /** Used as a safe reference for `undefined` in pre-ES5 environments. */
  var undefined;

  /** Used to compose bitmasks for wrapper metadata. */
  var PARTIAL_FLAG = 32;

  /**
   * Creates a function that invokes `func` with `partial` arguments prepended
   * to those provided to the new function. This method is like `_.bind` except
   * it does **not** alter the `this` binding.
   *
   * The `_.partial.placeholder` value, which defaults to `_` in monolithic
   * builds, may be used as a placeholder for partially applied arguments.
   *
   * **Note:** This method doesn't set the "length" property of partially
   * applied functions.
   *
   * @static
   * @memberOf _
   * @category Function
   * @param {Function} func The function to partially apply arguments to.
   * @param {...*} [partials] The arguments to be partially applied.
   * @returns {Function} Returns the new partially applied function.
   * @example
   *
   * var greet = function(greeting, name) {
   *   return greeting + ' ' + name;
   * };
   *
   * var sayHelloTo = _.partial(greet, 'hello');
   * sayHelloTo('fred');
   * // => 'hello fred'
   *
   * // using placeholders
   * var greetFred = _.partial(greet, _, 'fred');
   * greetFred('hi');
   * // => 'hi fred'
   */
  var partial = rest(function(func, partials) {
    var holders = replaceHolders(partials, partial.placeholder);
    return createWrapper(func, PARTIAL_FLAG, undefined, partials, holders);
  });

  return partial;
});