working over arrays with for loops in js

index.js

// summarized and added comments, original source: https://es6.io/ course by Wes Bos
// messing with the prototype
Array.prototype.myFunction = function(){
    // add some array functionality
};

// initialising our array
const names = ["Alice", "Foo", "Bar", "Jon Doe"];

// adding some further properties
names.furtherProperty = "Madness";

// normal for loop
// + : works as expected
// - : old school :P
for(let i = 0; i < names.length; i++){
    console.log(names[i]);
}
/*
 * Output =>
 * Alice
 * Foo
 * Bar
 * Jon Doe
 */

// foreach callback loop
// + : works as expected
// - : you cannot call break; or continue; like you would in a for loop (callback function, no real loop)
names.forEach(value => {
   console.log(value);
});
/*
 * Output =>
 * Alice
 * Foo
 * Bar
 * Jon Doe
 */

// for in loop
// + : nice syntactic sugar
// - : does iterate over content of array, added prototype functions and further properties
for(const i in names){
    console.log(names[i]);
}
/*
 * Output =>
 * Alice
 * Foo
 * Bar
 * Jon Doe
 * Madness
 * [Function]
 */

// for of loop
// + : nice syntactic sugar
// + : allows break; and continue;
// + : works as expected
for(const name of names){
    console.log(name);
}
/*
 * Output =>
 * Alice
 * Foo
 * Bar
 * Jon Doe
 */

// additionally, we can also access the index like that:
for ( const [i, name] of names.entries()){
    // we are iterating over the ArrayIterator 
    console.log(name); 
    console.log(i);
}