63 lines
1.5 KiB
JavaScript
63 lines
1.5 KiB
JavaScript
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'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 lazy = require('lazy-cache')(require);
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* // cache the call to `require('ansi-yellow')`
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* lazy('ansi-yellow', 'yellow');
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* // use `ansi-yellow`
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* console.log(lazy.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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Object.defineProperty(proxy, name, {
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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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try {
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return (cache[name] = fn(mod));
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} catch (err) {
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err.message = 'lazy-cache ' + err.message + ' ' + __filename;
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throw err;
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}
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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) { return str.toLowerCase(); }
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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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