Refactoring repeated if statement within if else block

Question

I have this if blocks where i have to test within on the same thing in both blocks :

   if (download !== 'true') {
     if(index == undefined){
       res.json(req.doc);
     }else{
       res.json(index)
     }
   } else {
     if(index == undefined){
       exports.download(res, req.doc);
     }else{
       res.json(index)
     }
   }

Is there a way to refactor it in a way in which i wouldn't repeat the same thing ?

Why is the value of download a string? Why are you using == and not === on index? — Benjamin Gruenbaum
– Benjamin Gruenbaum, Commented May 12, 2019 at 17:23
it's actually a string, i just named it index of an object given which is the name of it — brxnzaz
– brxnzaz, Commented May 12, 2019 at 17:25

T.J. Crowder · Accepted Answer · 2019-05-12 17:33:20Z

6

Since you do the same thing in both branches when index == undefined is false, just do that test first and invert it:

if (index != undefined) {
  res.json(index);
} else if (download !== 'true') {
  res.json(req.doc);
} else {
  exports.download(res, req.doc);
}

Side notes:

== undefined and != undefined will treat undefined and null the same way. If you don't want your conditions to treat null like undefined, use === and !==.
It's slightly odd that download is a string, although of course that does happen sometimes. If download is actually a boolean, then !== 'true' will always be true (because no boolean is ever strictly equal to a string). If it's a boolean, use if (download) or if (!download) rather than === true or !== true. If it is a string, beware of whitespace at the beginning or end and capitalization (' true' !== 'true' is true because of the space; 'True' !== 'true' is true because of the capital T). FWIW.

edited May 12, 2019 at 17:33

answered May 12, 2019 at 17:27

T.J. Crowder

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1 Comment

brxnzaz Over a year ago

oh it worked for me and thank you for the detailed explanation

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