TypeScript Generator Function

function* simpleGenerator() {
    yield 1;
    yield 2;
}

function* typedGenerator(): Generator<string, number, boolean> {
    // Yields a string, expects a boolean to be passed into next()
    const injectedValue: boolean = yield "Step 1"; 
    
    // Yields another string
    yield `Step 2 received: ${injectedValue}`; 
    
    // Returns a number when done
    return 42; 
}

const gen = typedGenerator();

// 1. Starts execution, pauses at the first yield.
// The argument to the first next() is always ignored.
const res1 = gen.next(); 
// res1: { value: "Step 1", done: false }

// 2. Resumes execution, injects `true` into `injectedValue`.
// Pauses at the second yield.
const res2 = gen.next(true); 
// res2: { value: "Step 2 received: true", done: false }

// 3. Resumes execution, hits the return statement.
const res3 = gen.next(false); 
// res3: { value: 42, done: true }

function* subGenerator(): Generator<number, void, unknown> {
    yield 2;
    yield 3;
}

function* mainGenerator(): Generator<number, void, unknown> {
    yield 1;
    yield* subGenerator(); // Delegates execution to subGenerator
    yield 4;
}
// mainGenerator yields: 1, 2, 3, 4