es6-obj-class-conversion-save-data-to-instance.js

export default class {
  
  initConfig() {
    this.config = // ... load a json file via AJAX, filesystem, etc. ...
    
    return this.config;
  },

  configSettingExists( key ) {
    // Search the config object for the key value
    let found = Object.keys( this.config ).indexOf( key )
    return found;
  }

  // ...

}