CODEWITHSUNDEEP
javascriptramda.js
Dinesh Verma
Dinesh Verma

Reputation: 666

conditionally return values using Ramda ifElse function

js and I am trying to learn it by trying to use that in my code in bits and pieces.

The problem I am trying to solve is to check if an object is null or not. If it is null then return a blank object else return the original object.

code written so far:

R.ifElse(isEmptyObj, R.always({}), R.always)({a:1})

Now the problem is if isEmpty return true, then R.always return a function that returns {}. But then isEmpty is false we want to return the same object passed to the function, so R.always get executed with that object so we get a function as output.

So, in one condition I get an object and in other I get a function.

Upvotes: 0

Views: 911

Answers (1)

Ori Drori
Ori Drori

Reputation: 193348

When R.always is called the 1st time with a value (let's call it X), it returns a 2nd function that will always return the value the 1st function was called with (X). Since you call the R.always without calling it first with a parameter, the result you get is the 2nd function.

In this case you want to pass the original value supplied to R.ifElse, so use R.identity:

const { ifElse, isNil, always, identity } = R

const fn = ifElse(isNil, always({}), identity)

console.log(fn({a:1})) // {a:1}
console.log(fn(null)) // {}
<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.27.1/ramda.min.js" integrity="sha512-rZHvUXcc1zWKsxm7rJ8lVQuIr1oOmm7cShlvpV0gWf0RvbcJN6x96al/Rp2L2BI4a4ZkT2/YfVe/8YvB2UHzQw==" crossorigin="anonymous"></script>

However, since you only want to return an empty object, if the original is null (or undefined if you use R.isNil), you can replace the R.ifElse with R.when. Using R.when the original value (the object) would be returned if the condition fails:

const { when, isNil, always } = R

const fn = when(isNil, always({}))

console.log(fn({a:1})) // {a:1}
console.log(fn(null)) // {}
<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.27.1/ramda.min.js" integrity="sha512-rZHvUXcc1zWKsxm7rJ8lVQuIr1oOmm7cShlvpV0gWf0RvbcJN6x96al/Rp2L2BI4a4ZkT2/YfVe/8YvB2UHzQw==" crossorigin="anonymous"></script>

Upvotes: 4

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