Closure CavesISSUE #27 of 61

generators · function* · yield

LambdaVSThe Mutator

Lambda saysGenerators (function*) pause and resume with yield, producing values lazily.

A function* returns a generator. Each yield hands back a value and pauses until next() is called again. This makes lazy sequences, infinite streams, and custom iterators trivial — and generators are iterable, so for...of and spread consume them directly.

Power-ups you unlock

function* + yield pauses/resumes
Produces values lazily, on demand
Generators are iterable
Great for streams and custom iteration

The Mutator attacks — common mistakes

Forgetting the * on function*
Spreading an infinite generator (locks up)
Expecting code after yield to run before next()

Boss battleWrite a generator that yields 1, 2, 3 and consume it with for...of.

Example code

<!doctype html><html><head><meta charset="utf-8"></head>
<body style="background:#06040d;color:#e6e0ff;font-family:monospace;padding:20px"><pre id="o"></pre>
<script>function* nums(){ yield 1; yield 2; yield 3; }
document.getElementById('o').textContent=[...nums()].join(' ');</script></body></html>

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