GT2/Ejectable/node_modules/any-promise/loader.js

79 lines
2.5 KiB
JavaScript

"use strict"
// global key for user preferred registration
var REGISTRATION_KEY = '@@any-promise/REGISTRATION',
// Prior registration (preferred or detected)
registered = null
/**
* Registers the given implementation. An implementation must
* be registered prior to any call to `require("any-promise")`,
* typically on application load.
*
* If called with no arguments, will return registration in
* following priority:
*
* For Node.js:
*
* 1. Previous registration
* 2. global.Promise if node.js version >= 0.12
* 3. Auto detected promise based on first sucessful require of
* known promise libraries. Note this is a last resort, as the
* loaded library is non-deterministic. node.js >= 0.12 will
* always use global.Promise over this priority list.
* 4. Throws error.
*
* For Browser:
*
* 1. Previous registration
* 2. window.Promise
* 3. Throws error.
*
* Options:
*
* Promise: Desired Promise constructor
* global: Boolean - Should the registration be cached in a global variable to
* allow cross dependency/bundle registration? (default true)
*/
module.exports = function(root, loadImplementation){
return function register(implementation, opts){
implementation = implementation || null
opts = opts || {}
// global registration unless explicitly {global: false} in options (default true)
var registerGlobal = opts.global !== false;
// load any previous global registration
if(registered === null && registerGlobal){
registered = root[REGISTRATION_KEY] || null
}
if(registered !== null
&& implementation !== null
&& registered.implementation !== implementation){
// Throw error if attempting to redefine implementation
throw new Error('any-promise already defined as "'+registered.implementation+
'". You can only register an implementation before the first '+
' call to require("any-promise") and an implementation cannot be changed')
}
if(registered === null){
// use provided implementation
if(implementation !== null && typeof opts.Promise !== 'undefined'){
registered = {
Promise: opts.Promise,
implementation: implementation
}
} else {
// require implementation if implementation is specified but not provided
registered = loadImplementation(implementation)
}
if(registerGlobal){
// register preference globally in case multiple installations
root[REGISTRATION_KEY] = registered
}
}
return registered
}
}