WeakMap

`WeakMap.prototype.set`

Adds or updates an element with a specified key and value to a WeakMap where the key must be an object or symbol

Syntax

JavaScript

weakMap.set(key, value)

Parameters

Parameter	Type	Description
key	object	The key of the element (must be an object)
value	any	The value of the element

Return Value

The WeakMap object (allows chaining)

Examples

Basic Usage

const wm = new WeakMap()
const key = {}
wm.set(key, 'metadata')
console.log(wm.get(key)) // 'metadata'

Practical Example

const privateData = new WeakMap<object, { count: number }>()
function createCounter() {
  const obj = {}
  privateData.set(obj, { count: 0 })
  return obj
}

Advanced Usage

const cache = new WeakMap<object, string>()
function expensive(obj: object) {
  if (cache.has(obj)) return cache.get(obj)!
  const result = JSON.stringify(obj)
  cache.set(obj, result)
  return result
}

Understanding WeakMap.prototype.set

The WeakMap.prototype.set method in JavaScript adds or updates an element with a specified key and value to a WeakMap where the key must be an object or symbol. It belongs to the WeakMap object and is one of the most widely used methods for working with weakmap values in modern JavaScript and TypeScript applications.

The method signature is weakMap.set(key, value). It accepts 2 parameters: key, value. When called, it returns the weakmap object (allows chaining). Understanding when and how to use set() helps you write more expressive, readable code.

Common use cases for WeakMap.prototype.set include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like weakmap-get, weakmap-has, weakmap-delete, enabling you to chain operations together for complex data manipulation pipelines.

Browser support for WeakMap.prototype.set is excellent across all modern browsers including Chrome, Firefox, Safari, and Edge. It is also fully supported in Node.js and Deno. For older environments, transpilation with Babel or a polyfill may be needed.