Discussion on: Stop using if else

[David Lazic]

With lookup maps approach you can drill down how much you wantt with minimal changes to the initial structure, so it would be something like this:

function isMorning () { ... }
function isSallyoffline () { ... }

function signIn(user, password) {
    const ALLOWED_USERS = {
      'bob': {
        pwd: '',
        isValid: () => true,
      },
      'sally': {
        pwd: 'gitIsCool7',
        isValid: () => isMorning,
      },
      'jerry': {
        pwd: 'hackme123',
        isValid: () => isSallyoffline,
      },
    };

    return ALLOWED_USERS[user] &&
           ALLOWED_USERS[user].pwd === password &&
           ALLOWED_USERS[user].isValid() ||
           'Whateva';
}

Now you can go even further and have multiple validity checks for example:

function isMorning () { ... }
function isSallyoffline () { ... }

function signIn(user, password) {
    const ALLOWED_USERS = {
      'bob': {
        pwd: '',
        validation: [
          () => true,
        ],
      },
      'sally': {
        pwd: 'gitIsCool7',
        validation: [
          () => isMorning,
        ],
      },
      'jerry': {
        pwd: 'hackme123',
        validation: [
          () => isMorning,
          () => isSallyoffline,
        ],
      },
    };

    return ALLOWED_USERS[user] &&
               ALLOWED_USERS[user].pwd === password &&
               ALLOWED_USERS[user].validation.every(rule => rule()) ||
               'Whateva';
}

And sorry for jumping in like so in the thread, I just know that plenty of people are for some reason struggling with this approach and I found this example intriguing. Also want to add that there is no practical way to completely avoid if/else statements, I use both approaches in my every day coding, it's just a matter of improving readability and removing code duplication.

If there's a simple 0 and 1 check, I see no reason to use a lookup map for that case, I'd just write down a simple if.

[Rishav Jadon]

This comment, and example is the best to explain the concept, thanks for this!

[naveennamani]

@davidlazic are you saying i should replace

a===10

with

example('a', a)

sure those are equivalent, but what above the functionality that i intended to run in the if condition, should I wrap them in anonymous functions and pass to another function. What about the else if condition? Should I call that like

if(example('b', b))

?
If all conditions has some common logic you can use mapping to bring the variability into the object and using the mapped values to execute the logic. But again, even if slight deviation is added (for example a console log in a single else if condition) then your common logic is not common anymore, and you have to add more hacks like anonymous functions as part of the mapping object and so on, as you just demonstrated in your example with validation functions.

The best practical example would be state management in redux, where switch case statements seems to be most efficient, readable and manageable, try implementing that with mapping.

[David Lazic]

Hey @naveennamani , appreciate the time you've taken to think about this. My comment was a reply, not a statement, where I simply described how a specific problem could be written in a different kind of way with an example. Like I wrote, I use if/else, switch and this kind of approach on every day basis, based on the situation. If a function is supplied with too much logic, there's probably something that's gonna go wrong and it could be split into separate pure parts.