What is the best way in ES6 to assign a constant conditionally?

Question

I would like to assign to my const validation a value based on a condition.

If this.showRequired() == true Then it should be 'required'

Else if this.showError() == true Then it should be 'error'.

I know of course that I could extract it to a function, or cascade ternary operators, but the first seems code bloat, the latter ugly.

Is there a better way to do it? If-else expressions maybe?

Answer 1

Cascading ternary operator looks fine for me:

const validation = this.showRequired() ? 'required' : this.showError() ? 'error' : null

If you think this line is too long, you could split it:

const validation = this.showRequired() ? 'required'
                   : this.showError() ? 'error'
                   : null

Or you could use && and || instead:

const validation = (this.showRequired() && 'required') ||
                   (this.showError() && 'error')

As for extacting this code into a separate function, you could always use an inline function instead of creating yet another class method:

const validation = (() => {
  if (this.showRequired()) {
    return 'required'
  } else if (this.showError()) {
    return 'error'
  }
})()

But ternary operator looks better anyway, especially if it's split into several lines.