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