68 lines
1.6 KiB
JavaScript
68 lines
1.6 KiB
JavaScript
'use strict';
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/**
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* Cache results of the first function call to ensure only calling once.
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*
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* ```js
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* var utils = require('lazy-cache')(require);
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* // cache the call to `require('ansi-yellow')`
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* utils('ansi-yellow', 'yellow');
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* // use `ansi-yellow`
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* console.log(utils.yellow('this is yellow'));
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* ```
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*
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* @param {Function} `fn` Function that will be called only once.
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* @return {Function} Function that can be called to get the cached function
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* @api public
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*/
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function lazyCache(fn) {
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var cache = {};
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var proxy = function(mod, name) {
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name = name || camelcase(mod);
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// check both boolean and string in case `process.env` cases to string
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if (process.env.UNLAZY === 'true' || process.env.UNLAZY === true || process.env.TRAVIS) {
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cache[name] = fn(mod);
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}
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Object.defineProperty(proxy, name, {
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enumerable: true,
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configurable: true,
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get: getter
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});
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function getter() {
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if (cache.hasOwnProperty(name)) {
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return cache[name];
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}
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return (cache[name] = fn(mod));
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}
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return getter;
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};
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return proxy;
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}
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/**
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* Used to camelcase the name to be stored on the `lazy` object.
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*
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* @param {String} `str` String containing `_`, `.`, `-` or whitespace that will be camelcased.
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* @return {String} camelcased string.
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*/
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function camelcase(str) {
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if (str.length === 1) {
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return str.toLowerCase();
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}
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str = str.replace(/^[\W_]+|[\W_]+$/g, '').toLowerCase();
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return str.replace(/[\W_]+(\w|$)/g, function(_, ch) {
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return ch.toUpperCase();
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});
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}
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/**
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* Expose `lazyCache`
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*/
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module.exports = lazyCache;
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