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Functional Programming Patterns With RamdaJS!

ifElse

Using ifElse in functional pipelines (3 min. read)

We'll cover the following...

We’re used to seeing if statements like this

Javascript (babel-node)
const hasAccess = true;
if (hasAccess) {
  console.log('Access granted.');
} else {
  console.log('Access denied.');
}

An increasingly popular alternative is the ternary statement.

Javascript (babel-node)
const hasAccess = true;
const message = hasAccess ? 'Access granted.' : 'Access denied.';
console.log(message);

Ramda provides ifElse, letting you handle branching logic with functions.

Javascript (babel-node)
import { ifElse } from 'ramda';
const hasAccess = true;
const logAccess = ifElse(
  () => hasAccess,
  () => console.log('Access granted.'),
  () => console.log('Access denied.')
);
logAccess();

One advantage is that you can package the logic away into a function. Instead of hardcoding the hasAccess variable, make it a parameter.

Javascript (babel-node)
import { ifElse } from 'ramda';
const logAccess = ifElse(
  (hasAccess) => hasAccess,
  () => console.log('Access granted.'),
  () => console.log('Access denied.')
);
logAccess(true);

And instead of the console.log side-effect, purify it by simply returning your desired result.

Javascript (babel-node)
import { ifElse } from 'ramda';
const logAccess = ifElse(
  (hasAccess) => hasAccess,
  () => 'Access granted.',
  () => 'Access denied.'
);
const result = logAccess(true);
console.log({ result });

This makes a point-free style easier to achieve.

Javascript (babel-node)
import { always, equals, ifElse } from 'ramda';
const logAccess = ifElse(
  equals(true),
  always('Access granted.'),
  always('Access denied.')
);
const result = logAccess(true);
console.log({ result });

And the end result’s easier to test!