Get key by value mit JavaScript

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Object.prototype.getKey = function(value){
  for(var key in this){
    if(this[key] == value){
      return key;
    }
  }
  return null;
};
 
// ISO 639: 2-letter codes
var languageCodes = {
  DA: 'Danish',
  DE: 'German',
  DZ: 'Bhutani',
  EL: 'Greek',
  EN: 'English',
  EO: 'Esperanto',
  ES: 'Spanish'
};
 
var key = languageCodes.getKey('Greek');
console.log(key); // EL

Object.prototype.getKey = function(value){ for(var key in this){ if(this[key] == value){ return key; } } return null; }; // ISO 639: 2-letter codes var languageCodes = { DA: 'Danish', DE: 'German', DZ: 'Bhutani', EL: 'Greek', EN: 'English', EO: 'Esperanto', ES: 'Spanish' }; var key = languageCodes.getKey('Greek'); console.log(key); // EL

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Object.prototype.getKey = function(value){
  for(var key in this){
    if(this[key] == value){
      return key;
    }
  }
  return null;
};
 
var companies = {}; // Object
companies["GD"] = "GameDuell";
companies["HP"] = "Hewlett-Packard Company";
companies["MS"] = "Microsoft";
 
for(var key in companies){
  console.log("Key: "+key+", Type: "+typeof(companies[key]));
  // Output:
  // Key: GD, Type: string
  // Key: HP, Type: string
  // Key: MS, Type: string
  // Key: getKey, Type: function | The function has become an element of the object!!
}

Object.prototype.getKey = function(value){ for(var key in this){ if(this[key] == value){ return key; } } return null; }; var companies = {}; // Object companies["GD"] = "GameDuell"; companies["HP"] = "Hewlett-Packard Company"; companies["MS"] = "Microsoft"; for(var key in companies){ console.log("Key: "+key+", Type: "+typeof(companies[key])); // Output: // Key: GD, Type: string // Key: HP, Type: string // Key: MS, Type: string // Key: getKey, Type: function | The function has become an element of the object!! }

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var BN = BN || {};
BN.Utilities = {};
BN.Utilities.getKey = function(value,object){
  for(var key in object){
    if(object[key] == value){
      return key;
    }
  }
  return null;
};
 
var companies = {};
companies["GD"] = "GameDuell";
companies["HP"] = "Hewlett-Packard Company";
companies["MS"] = "Microsoft";
 
for(var key in companies){
  console.log("Key: "+key+", Type: "+typeof(companies[key]));
  // Output:
  // Key: GD, Type: string
  // Key: HP, Type: string
  // Key: MS, Type: string
}
 
var key = BN.Utilities.getKey("GameDuell",companies);
console.log(key); // GD

var BN = BN || {}; BN.Utilities = {}; BN.Utilities.getKey = function(value,object){ for(var key in object){ if(object[key] == value){ return key; } } return null; }; var companies = {}; companies["GD"] = "GameDuell"; companies["HP"] = "Hewlett-Packard Company"; companies["MS"] = "Microsoft"; for(var key in companies){ console.log("Key: "+key+", Type: "+typeof(companies[key])); // Output: // Key: GD, Type: string // Key: HP, Type: string // Key: MS, Type: string } var key = BN.Utilities.getKey("GameDuell",companies); console.log(key); // GD