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Simple meta-programming for methods
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| /** | |
| * Intercept.js | |
| * Simple meta-programming for methods | |
| * Copyright (c) 2014 marlun78 | |
| * MIT License, https://gist.github.com/marlun78/bd0800cf5e8053ba9f83 | |
| * | |
| * The intercept-function provides a pre and a post hook that | |
| * will run before and after the original implementation | |
| * respectively. In the pre-hook you have access to the | |
| * arguments passed, and in the post-hook you have access to | |
| * both the arguments and the value returned by the original | |
| * implementation. | |
| * | |
| * @example | |
| * var math = { add: function add(a, b) { return a + b; } }; | |
| * var revert = intercept(math, 'add', pre, post); | |
| * function pre(config) { console.log('Pre', config); } | |
| * function post(config) { console.log('Post', config); } | |
| * math.add(1, 2); | |
| * // Pre, { args: [1, 2] } | |
| * // Post, { args: [1, 2], returned: 3 } | |
| * // 3 | |
| * revert(); | |
| * math.add(2, 3); | |
| * // 5 | |
| * | |
| * @param {Object} host - The object where the method lives in | |
| * @param {String} name - The name of the method to intercept | |
| * @param {Function} pre - A function to be called _before_ the original implementation | |
| * @param {Function} post - A function to be called _after_ the original implementation | |
| * @param {Boolean} once - Should this be reverted after the first call? | |
| * @returns {Function} - A revert function | |
| */ | |
| var intercept = (function () { | |
| 'use strict'; | |
| var slice = Array.prototype.slice; | |
| return function intercept(host, name, pre, post, once) { | |
| var originalMethod = host[name]; | |
| if (isFunction(originalMethod)) { | |
| host[name] = intercepted; | |
| return revert; | |
| } | |
| return noop; | |
| function intercepted() { | |
| var config = { args: toArray(arguments) }; | |
| if (once === true) revert(); | |
| if (isFunction(pre)) pre.call(this, config); | |
| config.returned = originalMethod.apply(this, config.args || []); | |
| if (isFunction(post)) post.call(this, config); | |
| return config.returned; | |
| } | |
| function revert() { | |
| host[name] = originalMethod; | |
| } | |
| }; | |
| function noop() {} | |
| function isFunction(value) { | |
| return typeof value === 'function'; | |
| } | |
| function toArray(value) { | |
| return slice.call(value); | |
| } | |
| }()); |
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