Generator

What is special about a generator function

Normal function

function normalFunction() {
  console.log("Hello");
  console.log("World");
}

Run to complemetion model.
Output: 'Hello' 'World'
Exit by returning or throwing an error.
If you call the function again, it will begin the execution from the top.

Generator function

function* generatorFunction() {
  yield `Hello`;
  yield `World`;
}

Warning

Do not forget the * after function key : function* generatorFunction()

A generator is a function that can stop midway and then continue from where it stopped.
A generator function can "pause" the execution.
To achieve that behaviour, we use the yield keyword.
yield is an operator with which a generator can pause itself.
Generator yields a value.

Invocation

Generators

Create the Generator

function* generatorFunction() {
  yield `Hello`;
  yield `World`;
}

const generatorObject = generatorFunction();

Use the Generator

for(const word of generatorObject) {
  console.log(word);
}
// Log: Hello world

console.log([...generatorObject]);
// Log: [ 'Hello', 'world' ]

generatorObject.next();
// Returns { value: ‘Hello’, done: false }

generatorObject.next();
// Returns { value: ‘World', done: false }

generatorObject.next();
// Returns { value: undefined, done: true }