nope-js-browser
Version:
NoPE Runtime for the Browser. For nodejs please use nope-js-node
60 lines (59 loc) • 2.37 kB
JavaScript
/**
* @author Martin Karkowski
* @email m.karkowski@zema.de
* @desc [description]
*/
const NOPE_SYMBOL = Symbol.for("nope");
const SINGLETONS_SYMBOL = Symbol.for("singletons");
/**
* Function to get a singleton. To create the singleton, the parameter *create* is used. This will be called once.
* The singleton will be stored as *global* variable and can be accessed by the identifier
*
* @author M.Karkowski
* @export
* @template T The Type of the singleton
* @param {string} identifier Identifier to access the singleton
* @param {() => T} create The Callback which is used to create the instance.
* @return An object, containing the key **instances**, where you'll find the instance and an helper function **setInstance** to redefine the instance
*/
export function getSingleton(identifier, create) {
if (!global[NOPE_SYMBOL]) {
global[NOPE_SYMBOL] = {
singletons: {},
};
}
if (!global[NOPE_SYMBOL][SINGLETONS_SYMBOL]) {
global[NOPE_SYMBOL][SINGLETONS_SYMBOL] = {};
}
// Extract all
const globalSingletons = Object.getOwnPropertyNames(global[NOPE_SYMBOL][SINGLETONS_SYMBOL]);
// create a unique, global symbol name
// -----------------------------------
const IDENTIFIER_DISPATCHER_CONTAINER = identifier;
// check if the global object has this symbol
// add it if it does not have the symbol, yet
// ------------------------------------------
const hasContainer = globalSingletons.indexOf(IDENTIFIER_DISPATCHER_CONTAINER) > -1;
if (!hasContainer) {
global[NOPE_SYMBOL][SINGLETONS_SYMBOL][IDENTIFIER_DISPATCHER_CONTAINER] =
create();
}
const ret = {
instance: global[NOPE_SYMBOL][SINGLETONS_SYMBOL][IDENTIFIER_DISPATCHER_CONTAINER],
setInstance: (value) => {
global[NOPE_SYMBOL][SINGLETONS_SYMBOL][IDENTIFIER_DISPATCHER_CONTAINER] =
value;
},
};
// define the singleton API
// ------------------------
Object.defineProperty(ret, "instance", {
get: function () {
return global[NOPE_SYMBOL][SINGLETONS_SYMBOL][IDENTIFIER_DISPATCHER_CONTAINER];
},
});
// ensure the API is never changed
// -------------------------------
Object.freeze(ret);
return ret;
}