🔰generator function

JS ⟩ iteration ⟩ generator function

defined by function* keyword and returns a Generator object.

syntax
use cases
- generator function as ... (variable, method)
- as make-iterator method of an iterable.
examples
- *list() - sequence of numbers
- *closedRange()
- *integers()
- *fibonacci()
composition of generator functions

yield and yield* operator can only be used within generator functions❗️

replit：yield must be in generator functions

// this seems like a generator function, but there's a catch ...
function* sequence(...iterables) {

    // --------------------------------------------------------------
    // ⭐ `yield/yield*` only available within generator functions❗
    // --------------------------------------------------------------
    
    // ❌ but this `yield*` is within an "arrow function"❗
    //
    //                 ╭─── 🔸 arrow function ───╮
    iterables.forEach( iterable => yield* iterable );
    //                             ^^^^^^
    // ⛔ ReferenceError: yield is not defined 
    
}

💾 replit：generator functions & objects

// ⭐️ generator function
function* abc() {
  yield 'a';
  yield 'b';
  yield 'c';
}

// main
let str = '';

// ⭐️ for-of loop  ╭───╮ ----> ⭐️ generator object
for (const char of abc()) {
  str += char;
}                  // str = 'abc'

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Last updated 3 years ago