How to return key of object with higher value in Javascript?

Question

Let’s say I have the following object:

var obj = {"frutas": 50, "vegetais": 100, "carnes": 150 };

How could I return the key of the highest value item? Example:

obj.maxKey(); // "carnes"

I tested some functions that deal with arrays, but apparently they do not work with objects in the pattern key: value, example:

Math.max.apply(null, meuArrayAqui);

So, how I could return the key of the highest value item?

Answer 1

There is no native function for this, so you will need to check all values to find the largest:

var obj = {"frutas": 50, "vegetais": 100, "carnes": 150 };
var maior = -Infinity;
var chave;
for(var prop in obj) {
    // ignorar propriedades herdadas
    if(obj.hasOwnProperty(prop)) { 
         if(obj[prop] > maior) {
             maior = obj[prop];
             chave = prop;
         }
    }
}
alert(chave);

That’s the principle. Of course, for real use, it’s better to wrap it in a function. Depending on the desired use, one can still do some optimizations.

Answer 2

The simplest way seems to me to be with a loop even, but if you seek a more functional alternative, it can be done as follows:

• Get all object keys by using Object.keys;
• Sort them in descending order of value (you need to use a custom function for this);
• Take the first element.

Example:

var obj = {"frutas": 50, "vegetais": 100, "carnes": 150 };

var maior = Object.keys(obj).sort(function(a,b) {
                return obj[a] > obj[b] ? -1 :
                       obj[b] > obj[a] ? 1 : 0;
            })[0];

document.querySelector("body").innerHTML += "<p>" + maior + "</p>";

Answer 3

Using the each of jQuery and traversing through all objects, can do as follows:

function getKeyOfMaxObjValue(obj){
  // Variável que armazenará a maior key.
  var key;
  // Variável auxiliar para checar os valores
  var value = 0;
  $.each(obj, function(idx, val){
    // Se o valor atual da iteração é maior que o auxiliar
    if(val > value){
      // Atualiza o valor da variável auxiliar
      value = val;
      // Atribue a nova key
      key = idx;
    }
  });
  return key;
}