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  1. -
  2. JavaScript
  3. JavaScript
  5. WeakMap
  6. WeakMap.prototype.get()
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WeakMap.prototype.get()

Baseline Widely available

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

get() WeakMap,

In this article

wm.get(key);

key

. , WeakMap.

undefined, WeakMap.

get

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

wm.get(window); //  "foo".
wm.get("baz"); //  undefined.

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

Firefox-specific notes

  • Prior to SpiderMonkey 38, this method threw a TypeError when the key parameter was not an object. However, the latest ES6 standard specifies to return undefined instead. Furthermore, WeakMap.prototype.get accepted an optional second argument as a fallback value, which is not part of the standard. Both non-standard behaviors are removed in version 38 and higher (Firefox bug 1127827).

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  2. WeakMap
    1. WeakMap()
    1. WeakMap.prototype.delete()
    2. WeakMap.prototype.get()
    3. getOrInsert()
    4. getOrInsertComputed()
    5. WeakMap.prototype.has()
    6. WeakMap.prototype.set()
  6. Object/Function
    1. Function.prototype.apply()
    2. Function.prototype.bind()
    3. Function.prototype.call()
    4. Function.prototype.toString()
    5. [Symbol.hasInstance]()
    1. Function.displayName
    2. Function.length
    3. Function.name
    4. prototype
    5. Function.arguments
    6. Function.caller
    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()
    1. Object.prototype.__proto__
    2. Object.prototype.constructor
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