JavaScript Understanding the Weird Parts - Array for in

index.js

const names = ['John', 'Jane', 'Joe']

for (let key in names) {
 console.log(key + ": " + names[key]); // array is an object with the key being the index 
}

Array.prototype.someNewProperty = 'abc';

// now we get the new property someNewProperty in the output as well. 
for (let key in names) {
 console.log(key + ": " + names[key]);
}

// The for of syntax available in ES6 fixes this.