change a prop in list of object in ramda.js

Question

I have an array of object in JSON and want to change one value's properties. for example assume I have a key field which is unique and amount , name props. my approach is to find an object in the list with findIndex or map then remove it and make a new object and push to it. is this good way? can recommend better approach or functions?

Answer 1

Lenses might be the canonical way to deal with this, although Ramda has a number of alternatives.

const people = [
  {id: 1, name: 'fred', age: 28},
  {id: 2, name: 'wilma', age: 25},
  {id: 3, name: 'barney', age: 27},
  {id: 4, name: 'betty', age: 29},  
]

const personIdx = name => findIndex(propEq('name', name), people)
const ageLens = idx => lensPath([idx, 'age'])

const wLens = ageLens(personIdx('wilma'))

const newPeople = over(wLens, age => age + 1, people)
//=> [
//     {id: 1, name: 'fred', age: 28},
//     {id: 2, name: 'wilma', age: 26},
//     {id: 3, name: 'barney', age: 27},
//     {id: 4, name: 'betty', age: 29},  
//   ]

Note that although newPeople is a brand new object, it shares as much as it can with the existing people . For instance, newPeople[3] === people[3] //=> true .

Also note that as well as adjusting a parameter with this lens using over , we could simply fetch the value using view :

view(wLens, people) //=> 25

Or we could set it to a fixed value with set :

set(wLens, 42, people) //=> new version of `people` with wilma's age at 42

Finally, note that lenses compose. We could have also written this:

const ageLens = idx => compose(lensIndex(idx), lensProp('age')).

Lens composition can be very powerful.

You can see this in action on the Rand REPL .

Answer 2

Something like this maybe?

var org = 
  [
    {name:"one",age:1}
    ,{name:"two",age:2}
  ]
;
var newArray =
  org
  .map(
    (x,index)=>
      index === 1
      ?Object.assign(
        {}
        ,x
        ,{name:"new name"}
      )
      :x
  )
;