ecma script 6 cheat cheet

es6-cheatsheet.js

/* for of loops and iterables */

for(let char/*can use destructuring here*/ of "hello"){
  console.log(char); // unicode char
}
for(let value of [1,2,3]){
  console.log(value);
}

/*for of is for iterable objects like arrays and collections like Map or Set, 
it's the workhorse loop statement introduced with es6*/
// Sets are a collection of unique values
// Maps are a collections of key and values
// these objects all include all a new property method "object[Symbol.iterator]" and "object[next]"
let iterator = [1,2,3][Symbol.iterator]();
console.log(iterator.next());

/*every object can be used for the for of loop but 
they need to have the iterator method */
for(let prop of Object.keys({name: 'rob'})){ // this returns an array which has the iterator method
  console.log(prop);
}

// an custom iterable object would look e.g. like this
var zeroesForeverIterator = {
  [Symbol.iterator]: function () {
    return this;
  },
  next: function () {
    return {done: false, value: 0};
  }
};

//“Good artists copy, great artists steal.” —Pablo Picasso

/* Generators */
/* They are special functions (see the function* keyword)
which construct asynchron function iterators */

function* CustomerServiceMessenger(name){
  let customerMessage = yield 'Hello '+name;
  console.log(customerMessage);
  customerMessage = yield 'Can you explain ?';
  console.log(customerMessage);
  customerMessage = yield 'Thank you and Goodbye!';
  console.log(customerMessage);
  return "[return value]" /* or some reference */;
  
}
let messenger = CustomerServiceMessenger('eimfach');
console.log("Press any key to call the CustomerServiceMessenger...");
window.addEventListener('keypress', function listener(e){
  console.clear();
  console.log('Calling...');
  window.removeEventListener('keypress', listener);
  window.addEventListener('keypress', function messageListener(e){
    let message = messenger.next('[customer message]');
    if(message.done !== true){
      console.log(message.value)
      //reply etc
    } else {
      console.log('Messaging done.', message.value);
      window.removeEventListener('keypress', messageListener);
    }
  });
});

/* Make any object iterable with generators 
(mind drop the default iterator interface implementation mentioned before)*/

var myIterable = {
  models: [1,2,3],
  [Symbol.iterator]: function*(){
    yield this;
  }
}

let iter = myIterable[Symbol.iterator]();
console.log(iter.next());

for(let {models} of myIterable){
  console.log(models)
}

let NumberDrawer = {
  [Symbol.iterator]: function*(){
    while(true){
        yield Math.floor(Math.random()*10);
    }  
  }
}

let drawer = NumberDrawer[Symbol.iterator]();

let sequence = [...Array(100)].map(val => drawer.next().value).join('')

console.log(sequence)

// Array to Object conversion using lodash and an arrow function
_.reduce(tags, (obj, tag) => _.extend(obj, {[tag]: false}), {})