is it possible to refactor and completely avoid many if else if else statements for better readability

Question

is it possible to refactor and completely avoid many if else if else statements for better readability. for example :

 function canIWatch(age) {
if (age < 6 && age > 0) return "You are not allowed to watch Deadpool after 6:00pm.";
else if (age >=6 && age < 17) return "You must be accompanied by a guardian who is 21 or older.";
else if (age >=17 && age < 25) return "You are allowed to watch Deadpool, right after you show some ID.";
else if (age >= 25 && age < 50 ) return "Yay! You can watch Deadpool with no strings attached!";
else if (age >= 50) return " You are too old to watch deadpool";
else return "Invalid age."
}

how can i write a much cleaner code without having this much if else statements

You don't need `age >= 25` and all other `>=` second checks. — zerkms, Nov 30 '16 at 20:31
Possible duplicate of [Switch on ranges of integers in JavaScript](http://stackoverflow.com/questions/5619832/switch-on-ranges-of-integers-in-javascript) — Geoff James, Nov 30 '16 at 20:32
@community: **please don't** close as duplicate. The checked and the second most upvoted answer from the "Switch on ranges of integers in JavaScript" are both terrible and actually an examples on how **NOT** to use `switch` — zerkms, Nov 30 '16 at 20:37
@zerkms That is not a good reason for declining to close as a duplicate. If you don't like the top answer, then write a comment or a competing answer, or put an upvote/bounty on a better existing answer. — 200_success, Nov 30 '16 at 20:54
@200_success it's a 5 years old answer with 117 positive upvotes. Nothing would beat it. But just because the question looks the same - it does not mean it must be closed as a dupe (especially when doing so helps spreading awkward practices). I'm not insisting though - do whatever you want (it's *your decision* whether *you* want newbies to see that as a solution or not). I prefer the Nina's answer *here* much more, hence I upvoted it. — zerkms, Nov 30 '16 at 20:57
@zerkms -- I'm not sure I agree with "spreading awkward practices". I will concur that different people's versions of "readability" can vary so much. But, in programming I would argue that a `switch` statement is (probably - where possible to use) a lot easier to read than a ton of if/else statements chained together. I agree with you on Nina's answer, hence why I upvoted it, also. — Geoff James, Nov 30 '16 at 21:00
@GeoffJames after writing code for more than 15 years - I struggle to remember at least one case when having the `switch-case` with reversing constant and expression parts was reasonable. But it's just my experience. `switch(true)` under no circumstances would pass my codereview. — zerkms, Nov 30 '16 at 21:02
@zerkms - I agree, it's very unorthadox - can't say I've ever had to use it myself, either! :) — Geoff James, Nov 30 '16 at 21:04

Nina Scholz · Accepted Answer · 2016-11-30T20:54:57.830

You could change the check and start with the smallest value and skip the else part, because you return.

function canIWatch(age) {
  if (age < 0) {
      return "Invalid age."
  }
  if (age < 6) {
      return "You are not allowed to watch Deadpool after 6:00pm.";
  }
  if (age < 17) {
      return "You must be accompanied by a guardian who is 21 or older.";
  }
  if (age < 25) {
      return "You are allowed to watch Deadpool, right after you show some ID.";
  }
  if (age < 50) {
      return "Yay! You can watch Deadpool with no strings attached!";
  }
  return "You are too old to watch deadpool";
}

console.log(canIWatch(-1));
console.log(canIWatch(2));
console.log(canIWatch(8));
console.log(canIWatch(20));
console.log(canIWatch(28));
console.log(canIWatch(60));

A different solution would be to use an array with objects for the terms

function canIWatch(age) {
    var terms = [
            { age: 0, text: "Invalid age." },
            { age: 6, text: "You are not allowed to watch Deadpool after 6:00pm." },
            { age: 17, text: "You must be accompanied by a guardian who is 21 or older." },
            { age: 25, text: "You are allowed to watch Deadpool, right after you show some ID." },
            { age: 50, text: "Yay! You can watch Deadpool with no strings attached!" },
            { age: Infinity, text: "You are too old to watch deadpool" },
        ],
        text;

    terms.every(function (a) {
        text = a.text;
        return a.age <= age;
    });
    return text;
}

console.log(canIWatch(-1));
console.log(canIWatch(2));
console.log(canIWatch(8));
console.log(canIWatch(20));
console.log(canIWatch(28));
console.log(canIWatch(60));

score 1 · Answer 2 · answered Nov 30 '16 at 20:35

do the fact that you use return you should at least avoid else if but use if only

  function canIWatch(age) {
    if (age < 6 && age > 0) return "You are not allowed to watch Deadpool after 6:00pm.";
    if (age >=6 && age < 17) return "You must be accompanied by a guardian who is 21 or older.";
    if (age >=17 && age < 25) return "You are allowed to watch Deadpool, right after you show some ID.";
    if (age >= 25 && age < 50 ) return "Yay! You can watch Deadpool with no strings attached!";
    if (age >= 50) return " You are too old to watch deadpool"; 
    return "Invalid age."
  }

is it possible to refactor and completely avoid many if else if else statements for better readability

2 Answers2