Nice cheat sheet, did notice some type errors on the first for Loop:
here's the corrected code:
for (var i = 0; i < 10; i++) {
console.log(i + ": " + i * 3 + "<br />");
}
let a = [1, 2, 3];
var sum = 0;
for (var i=0; i <a.length; i++) {
sum += a[i];
} // pasing an array
console.log(sum);