Editing Generator (computer programming) (section)

===ECMAScript===

[[ECMAScript|ECMAScript 6]] (a.k.a. Harmony) introduced generator functions.

An infinite Fibonacci sequence can be written using a function generator:

<syntaxhighlight lang="javascript">
function* fibonacci(limit) {
    let [prev, curr] = [0, 1];
    while (!limit || curr <= limit) {
        yield curr;
        [prev, curr] = [curr, prev + curr];
    }
}

// bounded by upper limit 10
for (const n of fibonacci(10)) {
    console.log(n);
}

// generator without an upper bound limit
for (const n of fibonacci()) {
    console.log(n);
    if (n > 10000) break;
}

// manually iterating
let fibGen = fibonacci();
console.log(fibGen.next().value); // 1
console.log(fibGen.next().value); // 1
console.log(fibGen.next().value); // 2
console.log(fibGen.next().value); // 3
console.log(fibGen.next().value); // 5
console.log(fibGen.next().value); // 8

// picks up from where you stopped
for (const n of fibGen) {
    console.log(n);
    if (n > 10000) break;
}
</syntaxhighlight>