Suppose that when iterating over numbers,
we want to get some digit from these numbers.
For example, we want to make a number be
displayed on the console if its first digit
is `1`

or `2`

.

I remind you that you can’t refer to the characters of a number directly, that is, it won’t work like this:

```
for (let i = 1; i <= 100; i++) {
if (i[0] == 1 || i[0] == 2) { // that won't work
console.log(i);
}
}
```

First you need to convert the number to a string and then get a certain character of the returned string, like this:

```
for (let i = 1; i <= 100; i++) {
let str = String(i); // converting number to string
if (str[0] === '1' || str[0] === '2') {
console.log(i);
}
}
```

Loop through the numbers from `10`

to `1000`

and output the first
digit of each number to the console.

Loop through the numbers from `10`

to `1000`

and output the sum of the
first and second digits of each number
to the console.

Loop through the numbers from `10`

to `1000`

and output those numbers
whose first digit is equal to `1`

.

Loop through the numbers from `10`

to `1000`

and display those numbers
whose sum of the first two
digits is `5`

.