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  1. Tecnologia Web para desenvolvedores
  2. JavaScript
  3. Referência 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. It’s been available across browsers since julho de 2015.

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

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

Obrigatório. A chave do elemento cuja presença deve ser verificada no objeto WeakMap.

Valor de retorno

Boolean

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

Exemplos

Utilizando o método has

js
var wm = new WeakMap(); wm.set(window, "foo"); wm.has(window); // retorna true wm.has("baz"); // retorna false

Especificações

Specification
ECMAScript® 2027 Language Specification
# sec-weakmap.prototype.has

Compatibilidade com navegadores

Enable JavaScript to view this browser compatibility table.

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This page was last modified on 17 de fev. de 2025 by MDN contributors.

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  1. Objetos Globais
  2. WeakMap
  3. Construtor
    1. WeakMap()
  4. Métodos de instância
    1. WeakMap.prototype.delete()
    2. WeakMap.prototype.get()
    3. getOrInsert()
    4. getOrInsertComputed()
    5. WeakMap.prototype.has()
    6. WeakMap.prototype.set()
  5. Herança
  6. Object/Function
  7. Métodos estáticos
    1. Function.prototype.apply()
    2. Function.prototype.bind()
    3. Function.prototype.call()
    4. Function.prototype.toString()
    5. [Symbol.hasInstance]()
  8. Propriedades estáticas
    1. Function.displayName
    2. Function.length
    3. Function.name
    4. prototype
    5. Function.arguments
    6. Function.caller
  9. Métodos de instância
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toString()
    10. Object.prototype.valueOf()
  10. Propriedades de instância
    1. Object.prototype.__proto__
    2. Object.prototype.constructor

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