Ramda: replace NULL values in json array

Question

We have a json array that has the form:

[
{id: 123, name: 'abc', symbol: 'xyz'},
{id: 456, name: 'def', symbol: null},
...
]

We are looking for a Ramda transformation that will replace all instances where the 'symbol' property is NULL, with a simple '' (empty string). Any ideas about how this can be done without getting into a forEach or for...next loop?

The answer from @Tomalak captures exactly what you need. But the general "without getting into a forEach or for...next loop" can generally be answered pretty straightforwardly. Here, what would you want to do in your loop? You want to transform each value into one without a null symbol. Boom! map. If instead you said, I want to find only those..., you know you'll likely want to filter. If you wanted to find the first one that matches, then find. If you want to combine them all into a single smooshed object, then reduce. That will cover a great majority of your looping needs. — Scott Sauyet
– Scott Sauyet, Commented Nov 17, 2017 at 19:14

Tomalak · Accepted Answer · 2017-11-17 19:01:04Z

2

const data = [
  {id: 123, name: 'abc', symbol: 'xyz'},
  {id: 456, name: 'def', symbol: null},
  // ...
];

const newData = R.map(R.over(R.lensProp('symbol'), R.defaultTo('')), data);

console.log(newData);

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.25.0/ramda.min.js"></script>

answered Nov 17, 2017 at 19:01

Tomalak

340k68 gold badges547 silver badges635 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Gatmando Over a year ago

Marking this as correct answer since it seems the most complete from a "functional" perspective. As well it allows me to hit other individual properties without having to address others I'm not concerned with. However the answers from 김재원 and mac also worked - thanks for the ideas!

Tomalak Over a year ago

@Gatmando You can always define something like const defaultPropTo = (prop, def) => R.over(R.lensProp(prop), R.defaultTo(def)) and then simply R.map(defaultPropTo('symbol', ''), data).

Jaewon · Accepted Answer · 2017-11-17 18:33:27Z

1

How about this?

R.map(({ symbol, ...otherProps }) => ({ ...otherProps, symbol: symbol || '' }))(arr);

answered Nov 17, 2017 at 18:33

Jaewon

1263 bronze badges

Comments

mac · Accepted Answer · 2017-11-17 18:49:23Z

1

You can use lensProp with set.

arr.map(o => R.set(R.lensProp('symbol'), o.symbol || '', o))

answered Nov 17, 2017 at 18:49

mac

8581 gold badge6 silver badges11 bronze badges

Collectives™ on Stack Overflow

Ramda: replace NULL values in json array

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related