fizzBuzz.js

for (var i = 1; i <= 100; i++) {
    var str = '';
    if (i % 3 === 0) str += 'Fizz';
    if (i % 5 === 0) str += 'Buzz';
    console.log(str || i);
}

// More correct way define str outside of loop
// either way gets hoisted to top of scope in this case 
// global environment, in browser the window object
var str;
for (var i = 1; i <= 100; i++) {
    str = '';
    if (i % 3 === 0) str += 'Fizz';
    if (i % 5 === 0) str += 'Buzz';
    console.log(str || i);
}