js generators better explained

generators.test.js

import "babel-polyfill";

import chai from 'chai'

chai.should()


function* justin() {
    /**
     * CALL # 1
     *   calls first yield -> runs expression nc(), returns 3.
     *   returns back from stack immediately  (ie. console.log 1-m never called)
     */
    var m = yield 3;
    console.log('1 - m ', m);

    
    /**
     * Call #2
     *   skips first yield statement
     *   calls console.log(1 - m) from above, moves to yield 5 statement
     *   returns from stack after calling yield 5
     */
    var m2 = yield 5;
    console.log('2 - m ', m);
    console.log('2 - m2 ', m2);

    /**
     * Call #3
     *   skips first yield statement
     *   skips second yield statement
     *   calls console.log 2-m
     *   calls console.log 2-m2
     *   And... holy shit it's not 7?? Because the yield has an expression passed into it which returns immediately before {7} is ever executed
     */
    var m3 = yield 7;
    console.log('3 - m ', m);
    console.log('3 - m2 ', m2);
    console.log('3 - m3 ', m3);

    /**
     * Note, m3 console.logs 3-m never called because yield expression 7 is returned on 3rd call
     */
}

function* idMaker(){
    let idx = 0;
    while (true) {
        let next = yield ++idx + Math.random()
        if(next === "reset") {
            idx = 0
        }
    }
}

describe("generators", function() {

    describe("justin function", function () {
        it("generates thing", function () {

            const gen = justin()

            console.log('value ', gen.next().value)
            console.log('value ', gen.next().value)
            console.log('value ', gen.next("holy shit, some other expression!").value)

        })
    })

    describe("idMaker function", function() {
        it("increments 1 + random until reset", function() {
            const idmaker = idMaker()
            console.log('idMaker ', idmaker.next().value)
            console.log('idMaker ', idmaker.next().value)
            console.log('idMaker ', idmaker.next().value)
            console.log('idMaker ', idmaker.next("reset").value)
            console.log('idMaker ', idmaker.next().value)
        })
    })
})