# Disadvantage in using classes in JavaScript

Suppose we have several classes for styling messages:

`.success { color: green; } .warning { color: orange; } .error { color: red; }`

Suppose we displayed a successful message in some element and assigned it the appropriate class for success:

`elem.classList.add('success');`

Let us now display an error message in the same element and assign it the appropriate class for an error:

`elem.classList.add('error');`

As a result, it will turn out that the element will have two classes that conflict with each other:

`<div id="elem" class="success error"> text </div>`

It turns out that before adding a new class, we will first have to remove the previous one:

`elem.classList.remove('success'); elem.classList.add('error');`

This is not very convenient, since we may not know what the previous class was there and we will have to remove all classes in a row:

`elem.classList.remove('success'); elem.classList.remove('warning'); elem.classList.add('error');`

Given an input. When focus is lost, check that no more than `9` characters have been entered into it. If so, color the input's border green, and if not, color it red.

← →
↑
en ru