A simplified version of Symbol.for() function

symbol-lookup.js

Symbol.prototype.for = (key) => {
  // Safely getting the global registry
  const symbolRegistry = window.symbolRegistry || {};
  
  // Checking if this symbol exists
  if (symbolRegisty.hasOwnProperty(key)) {
    return symbolRegistry[key];
  }
  
  // It does not, creating a new one
  const newSymbol = Symbol();
  symbolRegistry[key] = newSymbol;
  window.symbolRegistry = symbolRegistry;
  return newSymbol;
}