js generator

generators.js

// Generators are denoted using `function*` syntax
const myGenerator = function* () {
    console.log("a");
}

const iterator = myGenerator();
iterator.next(); // execute the generator's body, which displays "a"

// a generator that generates numbers
const numberGenerator = function* () {
    let n = 0;
    while(true) {
        yield n;
        n += 1;
        if (n === 4) break;
    }
}

const numberIter = numberGenerator();
console.log(numberIter.next())
console.log(numberIter.next())
console.log(numberIter.next())
console.log(numberIter.next())
console.log(numberIter.next())

// for...of over an iterator
const numberIter2 = numberGenerator();
for (number of numberIter2) {
    console.log(number);
}

// delegating yield: yield another generator
const foo = function* () {
    yield 1;
    yield * bar();
}

const bar = function* () {
    yield 2;
}

for (item of foo()){
    console.log(item);
} // output: 1, 2

// iterator can throw values to its generator
const myGenerator2 = function* () {
    try {
        yield 1
    } catch (e) {
        if (e === 'a') {
            console.log("caught a");
        } else {
            throw e
        }
    }
}

const myIter2 = myGenerator();
myIter2.throw('a'); // output: caught a