Functions or character strings can be passed as arguments to SetTimeout() and setInterval(). In keeping with the previous best practice, using eval() and thus passing character strings is not recommended. Furthermore, if the argument passed is a string, it has to be evaluated by the interpreter before being converted into code. On the other hand, if this argument is a function or a reference to a function, no evaluation is needed, reducing CPU usage.

JavaScript allows for anonymous functions, and these should be used whenever possible without putting the project’s maintainability at risk. This way, the interpreter no longer needs to resolve the function’s name.
Be aware that this is only good practice when the function is used once. Any function used more than once should be named.