Generator Functions
A generator function (declared with function*) returns a Generator object. It can pause and resume execution using yield.
function* numberGenerator() {
yield 1;
yield 2;
yield 3;
}
const gen = numberGenerator();
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().done);The yield Keyword
yield pauses the generator and returns a value. The generator resumes when next() is called again.
function* countUpTo(limit) {
let count = 1;
while (count <= limit) {
yield count;
count++;
}
}
const counter = countUpTo(3);
for (const value of counter) {
console.log(value);
}Passing Values to next()
You can send a value back into the generator by passing an argument to next(). It replaces the yield expression.
function* interactive() {
const name = yield "What is your name?";
yield "Hello, " + name;
const age = yield "How old are you?";
yield name + " is " + age + " years old";
}
const it = interactive();
console.log(it.next().value);
console.log(it.next("Alice").value);
console.log(it.next().value);
console.log(it.next("30").value);