# else if construct in JavaScript

The `else if` construct allows you to set conditions in the `else` block. Let's look at an example:

`let num = 1; if (num == 1) { console.log('value1'); } else if (num == 2) { console.log('value2'); } else if (num == 3) { console.log('value3'); }`

The advantage of using `else if` instead of several ifs is the ability to catch the situation when the value of the variable `num` does not match any of the conditions:

`let num = 1; if (num == 1) { console.log('value1'); } else if (num == 2) { console.log('value2'); } else if (num == 3) { console.log('value3'); } else { console.log('incorrect value of the variable num'); }`

The variable `day` contains some number in the range from `1` to `31`. Determine in which decade of the month this number falls (in the first, second or third).

Modify the previous task so that if the variable `day` is not a number from `1` to `31`, an error message would be issued.

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