whay generate() do in js code example

Example 1: generators in javascript

function* g(){    //or function *g(){}
  console.log("First");
  yield 1;
  console.log("second");
   yield 2;
  console.log("third");
} 
let generator=g();
generator.next();
generator.next();

Example 2: JavaScript — Generators

function* makeRangeIterator(start = 0, end = 100, step = 1) {
    let iterationCount = 0;
    for (let i = start; i < end; i += step) {
        iterationCount++;
        yield i;
    }
    return iterationCount;
}