| var createWrapper = require('../internal/createWrapper'), |
| replaceHolders = require('../internal/replaceHolders'), |
| restParam = require('./restParam'); |
| |
| /** Used to compose bitmasks for wrapper metadata. */ |
| var BIND_FLAG = 1, |
| BIND_KEY_FLAG = 2, |
| PARTIAL_FLAG = 32; |
| |
| /** |
| * Creates a function that invokes the method at `object[key]` and prepends |
| * any additional `_.bindKey` arguments to those provided to the bound function. |
| * |
| * This method differs from `_.bind` by allowing bound functions to reference |
| * methods that may be redefined or don't yet exist. |
| * See [Peter Michaux's article](http://peter.michaux.ca/articles/lazy-function-definition-pattern) |
| * for more details. |
| * |
| * The `_.bindKey.placeholder` value, which defaults to `_` in monolithic |
| * builds, may be used as a placeholder for partially applied arguments. |
| * |
| * @static |
| * @memberOf _ |
| * @category Function |
| * @param {Object} object The object the method belongs to. |
| * @param {string} key The key of the method. |
| * @param {...*} [partials] The arguments to be partially applied. |
| * @returns {Function} Returns the new bound function. |
| * @example |
| * |
| * var object = { |
| * 'user': 'fred', |
| * 'greet': function(greeting, punctuation) { |
| * return greeting + ' ' + this.user + punctuation; |
| * } |
| * }; |
| * |
| * var bound = _.bindKey(object, 'greet', 'hi'); |
| * bound('!'); |
| * // => 'hi fred!' |
| * |
| * object.greet = function(greeting, punctuation) { |
| * return greeting + 'ya ' + this.user + punctuation; |
| * }; |
| * |
| * bound('!'); |
| * // => 'hiya fred!' |
| * |
| * // using placeholders |
| * var bound = _.bindKey(object, 'greet', _, '!'); |
| * bound('hi'); |
| * // => 'hiya fred!' |
| */ |
| var bindKey = restParam(function(object, key, partials) { |
| var bitmask = BIND_FLAG | BIND_KEY_FLAG; |
| if (partials.length) { |
| var holders = replaceHolders(partials, bindKey.placeholder); |
| bitmask |= PARTIAL_FLAG; |
| } |
| return createWrapper(key, bitmask, object, partials, holders); |
| }); |
| |
| // Assign default placeholders. |
| bindKey.placeholder = {}; |
| |
| module.exports = bindKey; |