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WeakMap.prototype.has() - JavaScript | MDN
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  1. Tecnologia Web para desenvolvedores
  2. JavaScript
  3. Referncia JavaScript
  4. Objetos Globais
  5. WeakMap
  6. WeakMap.prototype.has()
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WeakMap.prototype.has()

Baseline Widely available

This feature is well established and works across many devices and browser versions. Its been available across browsers since julho de 2015.

O mtodo has() retorna um booleano indicando se um elemento com a chave especificada existe no objeto WeakMap ou no.

In this article

Experimente

const weakmap1 = new WeakMap();
const object1 = {};
const object2 = {};

weakmap1.set(object1, "foo");

console.log(weakmap1.has(object1));
// Expected output: true

console.log(weakmap1.has(object2));
// Expected output: false

Sintaxe

wm.has(chave);

Parameters

chave

Obrigatrio. A chave do elemento cuja presena deve ser verificada no objeto WeakMap.

Valor de retorno

Boolean

Retorna true se um elemento com a chave especificada existir no objeto WeakMap. Caso contrrio, retorna false.

Exemplos

Utilizando o mtodo has

js
var wm = new WeakMap();
wm.set(window, "foo");

wm.has(window); // retorna true
wm.has("baz"); // retorna false

Especificaes

Specification
ECMAScript 2027 LanguageSpecification
# sec-weakmap.prototype.has

Compatibilidade com navegadores

Ver tambm

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  1. Objetos Globais
  2. WeakMap
  3. Construtor
    1. WeakMap()
  4. Mtodos de instncia
    1. WeakMap.prototype.delete()
    2. WeakMap.prototype.get()
    3. getOrInsert()
    4. getOrInsertComputed()
    5. WeakMap.prototype.has()
    6. WeakMap.prototype.set()
  5. Herana
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  7. Mtodos estticos
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  9. Mtodos de instncia
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  10. Propriedades de instncia
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