JavaScript 'For Loops'

A little glimpse into JavaScript 'For Loops'. 

Code:

arr = ['Fortran', 'Python', 'C++', 'Assembly', 'Binary'];

for (x in arr) {

document.write(x);

}

document.write('<br>');

for (var i = 0; i < arr.length; i++) {

document.write(i);

}

document.write('<br>');

for (x of arr) {

document.write(x + ' ');

}

document.write('<br>');

for (var i = 0; i < arr.length; i++) {

document.write(arr[i] + ' ');

}

Result:

01234
01234
Fortran Python C++ Assembly Binary
Fortran Python C++ Assembly Binary