74 lines
1.6 KiB
JavaScript
74 lines
1.6 KiB
JavaScript
'use strict';
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var set = require('set-getter');
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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(requireFn) {
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var cache = {};
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return function proxy(name, alias) {
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var key = alias;
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// camel-case the module `name` if `alias` is not defined
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if (typeof key !== 'string') {
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key = camelcase(name);
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}
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// create a getter to lazily invoke the module the first time it's called
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function getter() {
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return cache[key] || (cache[key] = requireFn(name));
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}
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// trip the getter if `process.env.UNLAZY` is defined
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if (unlazy(process.env)) {
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getter();
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}
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set(proxy, key, getter);
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return getter;
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};
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}
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/**
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* Return true if `process.env.LAZY` is true, or travis is running.
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*/
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function unlazy(env) {
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return env.UNLAZY === 'true' || env.UNLAZY === true || env.TRAVIS;
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}
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/**
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* Camelcase the the given module `name`.
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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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