Iterables & Loops

First some already established for-loops and in the end the new of-loop with some examples.

The old loops and the disadvantage

// Array for all example codes
const cuts = ['Chuck', 'Brisket', 'Shank', 'Short Rib'];

// Ugly syntax
for (let i = 0; i < cuts.length; i++) {
   console.log(cuts[i]);
}

// No way to break out of the loop
cuts.forEach((cut) => {
   console.log(cut);
   if(cut === 'Brisket') {
     continue;
   }
});

// Displays alternations to the prototype (added functions i.e.)
for (const index in cuts) {
   console.log(cuts[index]);
}

The for-of-loop

The for-of-loop is nearly always usable, except for iterating objects:

for (const cut of cuts) {
    if(cut === 'Brisket') {
      continue;
    }
    console.log(cut);
}

// Gives value and index and gets instantly destructured
// .entries() is ES7, you could use the in-loop instead
for (const [i, cut] of cuts.entries()) {
   console.log(`${cut} is the ${i + 1} item`);
}

// If you don't now the number of arguments comming in
function addUpNumbers() {
   let total = 0;
   for (const num of arguments) {
     total += num;
   }
   console.log(total);
   return total;
}
addUpNumbers(10,23,52,34,12,13,123);

Iterate an object

// Object
const apple = {
    color: 'Red',
    size: 'Medium',
    weight: 50,
    sugar: 10
};

for (const prop in apple) {
    const value = apple[prop];
    console.log(value, prop);
}

// not ready yet? (ES7)
for (const propp of apple.entries()) {
    console.log(propp);
}