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'use strict';
var set = require('set-getter');
/**
* Cache results of the first function call to ensure only calling once.
*
* ```js
* var utils = require('lazy-cache')(require);
* // cache the call to `require('ansi-yellow')`
* utils('ansi-yellow', 'yellow');
* // use `ansi-yellow`
* console.log(utils.yellow('this is yellow'));
* ```
*
* @param {Function} `fn` Function that will be called only once.
* @return {Function} Function that can be called to get the cached function
* @api public
*/
function lazyCache(requireFn) {
var cache = {};
return function proxy(name, alias) {
var key = alias;
// camel-case the module `name` if `alias` is not defined
if (typeof key !== 'string') {
key = camelcase(name);
}
// create a getter to lazily invoke the module the first time it's called
function getter() {
return cache[key] || (cache[key] = requireFn(name));
}
// trip the getter if `process.env.UNLAZY` is defined
if (unlazy(process.env)) {
getter();
}
set(proxy, key, getter);
return getter;
};
}
/**
* Return true if `process.env.LAZY` is true, or travis is running.
*/
function unlazy(env) {
return env.UNLAZY === 'true' || env.UNLAZY === true || env.TRAVIS;
}
/**
* Camelcase the the given module `name`.
*/
function camelcase(str) {
if (str.length === 1) {
return str.toLowerCase();
}
str = str.replace(/^[\W_]+|[\W_]+$/g, '').toLowerCase();
return str.replace(/[\W_]+(\w|$)/g, function(_, ch) {
return ch.toUpperCase();
});
}
/**
* Expose `lazyCache`
*/
module.exports = lazyCache;
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