How to stop writing chain code?

Question

for example...

if ( /* Condition */ ) {

    if ( /* Condition */ ) {

        if ( /* Condition */ ) {

          // Superb!

        } else {

          // Error 3

        }

    } else {

      // Error 2

    }

} else {

  // Error 1

}

Do you know how to avoid this? Thank you!

Answer 1

If this is a library function, throw may be the appropriate action.

if (!condition1) {
    throw "Condition 1 failed.";
}

if (!condition2) {
    throw "Condition 2 failed.";
}

if (!condition3) {
    throw "Condition 3 failed.";
}

// Superb!

Other acceptable actions might be:

• Returning 0, null, or undefined.
• Displaying an error to the user and returning.

You will have to determine which failure action is right for your use case.

Answer 2

It looks like you have 3 conditions to check and 4 actions (3 different errors + 1 success). Unfortunately in the general case it's going to require 3 conditional checks and 4 actions. I think the code can be cleaned up a bit by using the following structure though

if (! /* condition 1 */ ) {
  // Error 1
} else if (! /* condition 2 */ ) { 
  // Error 2
} else if (! /* condition 3 */ ) { 
  // Error 3
} else {
  // superb
}