Yes there is a utility called classnames
https://github.com/JedWatson/classnames
classNames('foo', 'bar'); // => 'foo bar'
classNames('foo', { bar: true }); // => 'foo bar'
classNames('foo', { bar: true, duck: false }, 'baz', { quux: true }); // => 'foo bar baz quux'
For your specific usage
const klassNames = classNames(`${class1} ${class2}`);
div><Link to = 'auth' className= {klassNames} >Login</Link></div>
I agree you might say this is the same as your previous code but see if want to add classes based on some conditions this is highly beneficial
Another Example
const klassNames = classNames(`${class1}`, {
`${class2}`: someCondition === true,
`${class3}: someCondition === false
}
I am using in my large react project really solves if else conditioning for classes
Example