Iterator.prototype[Symbol.dispose]()

The [Symbol.dispose]() method of Iterator instances implements the disposable protocol and allows it to be disposed when used with using. It calls the return() method of this, if it exists.

Syntax

js
iterator[Symbol.dispose]()

Parameters

None.

Return value

None (undefined).

Examples

undefined

Declaring an iterator with using

The Symbol.dispose method is intended to be automatically called in a using declaration. This is useful if you have an iterator that you manually iterate over by calling its next() method; if you iterate it with for...of or something similar, then error handling and cleanup is done automatically.

js
function* generateNumbers() {
  try {
    yield 1;
    yield 2;
    yield 3;
  } finally {
    console.log("Cleaning up");
  }
}

function doSomething() {
  using numbers = generateNumbers();
  const res1 = numbers.next();
  // Not iterating the rest of the numbers
  // Before the function exits, the async iterator is disposed
  // Logs "Cleaning up"
}

doSomething();

Specifications

See also