How to set an equal value for an object property on all objects in a list?

Question

How to set a value for a property in all list indices without looping?

object:

var objeto = {
  nome: "",
  ativo: false
}

list:

[{"nome": "Carlos","ativo":false},{"nome": "Joao","ativo":false}]

In this example, everyone should have the active property changed to true.

The way it solves:

    for (var i in lista) {
         lista[i].ativo = true;        
    }

Is there any way to avoid that loop, make that change all at once? because in actual application the object is more complex and has many records, leaving this method slow.

Answer 1

Considering the entry:

let data = [
    {"nome": "Carlos","ativo": false},
    {"nome": "Joao","ativo": false}
];

In the ES6 standard, you can use Object.assign to merge two objects. See:

// Dados de entrada:
let data = [
    {"nome": "Carlos", "ativo": false},
    {"nome": "Joao", "ativo": false}
];

// Altera todos os objetos da lista:
data = data.map(obj => Object.assign(obj, {"ativo": true}));

// Exibe o resultado:
console.log(data);

If you do not want to use this method, you can make the change in the hand:

// Dados de entrada:
let data = [
    {"nome": "Carlos", "ativo": false},
    {"nome": "Joao", "ativo": false}
];

// Altera todos os objetos da lista:
data = data.map(obj => {
  obj.ativo = true;
  return obj;
});

// Exibe o resultado:
console.log(data);

A benchmark shows that doing the for directly is faster, followed by the second solution present here and finally the solution using the method assign. That is, you save some characters, but lose in efficiency. In this case, as it is simple, there is no reason not to use your own for.