What is the definition of delete in Javascript?

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5

I came across an instruction that delete represents a type in Javascript. At least that’s what I understood.

I’d like your help because I couldn’t find any references on the Internet.

if (MvL.object.hasValue(domain.cpf) || MvL.object.hasValue(domain.cnpj)) {
  delete domain.nome_cliente;
  delete domain.cod_cgl;
  delete domain.uf;
}
javascript characteristic-language objects operators delete

  • References on the intenet have a number: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/delete. Here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/delete

2 answers

5


The delete not a guy, but a operator that removes a property from an object. However, it will only work on properties that have the property attribute [[Configurable]] defined as true. Behold:

const obj = {};
obj.name = 'Luiz';
Object.defineProperty(obj, 'lastName', {
  enumerable: true,
  configurable: false // Não irá permitir que deletemos a propriedade `lastName`.
});

console.log(obj); 
delete obj.name;
delete obj.lastName;
console.log(obj);

In normal Javascript mode, if you try to delete a non configurable property, false will be returned. However, if you are on strictly speaking, an error will be cast:

'use strict';

const obj = {};
Object.defineProperty(obj, 'lastName', {
  enumerable: true,
  configurable: false
});

delete obj.lastName; // Uncaught TypeError: Cannot delete property 'lastName'

That operator will return true in all cases, except when you try to remove a non configurable property without being in strict mode - we have already seen that, in the latter case, an error is launched.

If, even in strict mode, you want to receive a boolean false if you were unable to delete the property, you can use the method Reflect.deleteProperty, entered in Ecmascript 2015 (ES6):

'use strict';

const obj = {};
obj.name = 'Luiz';
Object.defineProperty(obj, 'lastName', {
  enumerable: true,
  configurable: false
});

console.log(obj); 
console.log(Reflect.deleteProperty(obj, 'name')); // true
console.log(Reflect.deleteProperty(obj, 'lastName')); // false
console.log(obj);

It is worth saying that both delete how much Reflect.deleteProperty will return true even if the property you try to delete does not exist.

To deepen on the operator delete, is worth reading the article "Understanding delete". More advanced details and algorithm can be found in specification.

0

Take a look at this example:

var person = {
    name: "Harry",
    age: 16,
    gender: "Male"
};

// Deleta a propriedade completamente
delete person.age;
alert(person.age); // Saida: undefined
console.log(person); // Saida: {name: "Harry", gender: "Male"}

// Definindo propriedade como undefined
person.gender = undefined;
alert(person.gender); // Saida: undefined
console.log(person); // Saida: {name: "Harry", gender: undefined}

The delete remove the object property, if you only need to change the property value the example also shows how to change the value.

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