Why flag parameters suck

When coding people tend to use flag parameters to drive their functions, without considering that they absolutely suck! They cause more trouble when a you write complex functions or a codebase that is large in nature, because the readability is just terrible let me explain.

What is a flag parameter?

A flag parameter is a Boolean that drives a function, for example:

function register(user, isAdmin) {
    if (isAdmin) {
        // give admin privs
    } else {
        //Give standard privs
    }
}

register(user, true);

The problem when using a flag parameter you lose context behind the parameter and another developer has to read through the full function before understanding what isAdmin is for. Now imagine that this function is complex making it hard to follow.

What is the alternative?

There are some alternatives to this issue but I prefer two options.

Create distinct functions

The first option create two functions that separate the flag, so taking above we can create:

function registerAdmin(user) {
    // do admin privs
}

function registerUser(user) {
    // give standard pribs
}

registerAdmin(user);
registerUser(user);

Now we have very distinct functions and based just upon the name we know exactly what is happening in the functions.

Using an options parameter

The second option, to use an options parameter that holds all the different parameters that drive the functions:

function register(user, options){
	if(options.admin){
	// do admin privs
}
else{
	//Give standard privs
}
}

register(user, options:{"admin" : true})

This option allows you to see what is driving the function without needing to read a full function, you can see there are extra options and are they an admin or not.