CODEWITHSUNDEEP
javascriptarraysramda.js
Rishabh Srivastava
Rishabh Srivastava

Reputation: 11

Ramda on arrays in javascript

  var censusMembers = Object.freeze([
    {
    id: 1,
    name: 'Bob'
    }, {
    id: 2,
    name: 'Sue'
    }, {
    id: 3,
    name: 'Mary',
    household_id: 2
    }, {
    id: 4,
    name: 'Elizabeth',
    household_id: 6
    }, {
    id: 5,
    name: 'Tom'
    }, {
    id: 6,
    name: 'Jill'
    }, {
    id: 7,
    name: 'John',
    household_id: 6
    }
    ]);

This is my array I want to count the number of elements which has household id using ramda function ? how can i do that ?

Upvotes: 1

Views: 271

Answers (3)

Ori Drori
Ori Drori

Reputation: 193037

You can also use R.countBy to count all items that have/don't have household_id using R.has(), and than get the count for true using R.prop():

const { pipe, countBy, has, prop } = R;

const censusMembers = Object.freeze([{"id":1,"name":"Bob"},{"id":2,"name":"Sue"},{"id":3,"name":"Mary","household_id":2},{"id":4,"name":"Elizabeth","household_id":6},{"id":5,"name":"Tom"},{"id":6,"name":"Jill"},{"id":7,"name":"John","household_id":6}]);

const countHouseholders = pipe(
  countBy(has('household_id')),
  prop('true'),
);

const result = countHouseholders(censusMembers);

console.log(result);
<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.25.0/ramda.js"></script>

Upvotes: 3

Ele
Ele

Reputation: 33736

Don't use the function filter to count stuff because you're creating an array only to get the length.

You can use the function R.reduce and within the handler, check for the key household_id

var censusMembers = Object.freeze([{id: 1,name: 'Bob'}, {id: 2,name: 'Sue'}, {id: 3,name: 'Mary',household_id: 2}, {id: 4,name: 'Elizabeth',household_id: 6}, {id: 5,name: 'Tom'}, {id: 6,name: 'Jill'}, {id: 7,name: 'John',household_id: 6}]);

// With household_id
//                                      (true is coerced to 1) = 1
console.log("With:", R.reduce((a, c) => ('household_id' in c) + a, 0, censusMembers));

// Without household_id
//                                         !(false is coerced to 0) = 1
console.log("Without:", R.reduce((a, c) => !('household_id' in c) + a, 0, censusMembers));
.as-console-wrapper { max-height: 100% !important; top: 0; }
<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.25.0/ramda.js"></script>

Upvotes: 0

Scott Sauyet
Scott Sauyet

Reputation: 50807

has looks to be what you're missing:

var censusMembers = Object.freeze([
  {id: 1, name: 'Bob'}, 
  {id: 2, name: 'Sue' }, 
  {id: 3, name: 'Mary', household_id: 2 }, 
  {id: 4, name: 'Elizabeth', household_id: 6},
  {id: 5, name: 'Tom'}, 
  {id: 6, name: 'Jill'}, 
  {id: 7, name: 'John', household_id: 6}
]);

const countHouseholders = R.pipe(R.filter(R.has('household_id')), R.length)

console.log(countHouseholders(censusMembers))
.as-console-wrapper { max-height: 100% !important; top: 0; }
<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.25.0/ramda.js"></script>

Upvotes: 0

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