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How to use the lens function from ramda

Find comprehensive JavaScript ramda.lens code examples handpicked from public code repositorys.

ramda.lens is a function used to create a lens, which is a way to view and modify data structures.

normalizeConfig.js

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const coerceUserOption = R.when(
  R.propSatisfies(R.complement(R.isNil), 'user'),
  R.compose(
    R.dissoc('user'),
    R.over(
      R.lens(updateHeaderWithUser, R.assoc('header')),
      R.identity
    )
  )
);

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+ 7 other calls in file

ramda.js

GitHub: corporatepiyush/es6

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{
    // lenses


    const xLens = _.lens(_.prop('x'), _.assoc('x'))


    _.view(xLens, {
        x: 1,
        y: 2

How does ramda.lens work?

In functional programming, a lens is a way to view and modify a portion of a data structure without modifying the structure itself. Lenses are often used in functional programming to provide a more composable way to work with immutable data. In Ramda, a lens is created using the ramda.lens function. The ramda.lens function takes two arguments: a getter function and a setter function. The getter function is used to retrieve the value of the portion of the data structure that the lens is focused on, and the setter function is used to update the value of that portion of the data structure. Here's an example of how to use ramda.lens to create a lens that focuses on a particular property of an object: javascript Copy code {{{{{{{ const { lens, prop, assoc } = require('ramda'); const myLens = lens(prop('myProperty'), assoc('myProperty')); const myObject = { myProperty: 'hello' }; console.log(myLens.get(myObject)); // Output: 'hello' const updatedObject = myLens.set(myObject, 'world'); console.log(updatedObject); // Output: { myProperty: 'world' } In this example, we use ramda.lens to create a lens that focuses on the myProperty property of an object. We use the prop and assoc functions to create the getter and setter functions for the lens, respectively. We then use the get method of the lens to retrieve the value of the myProperty property of an object, and the set method of the lens to update the value of the myProperty property of an object. Overall, ramda.lens provides a powerful way to work with data structures in a functional and composable way.

tests.js

GitHub: tyankatsu0105/design-patterns

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});




QUnit.test("Combining map and reduce with lenses", function () {
	const cityPath = ['address','city'];
	const cityLens = R.lens(R.path(cityPath), R.assocPath(cityPath));
	const gatherStats = (stat, criteria) => {
		stat[criteria] = _.isUndefined(stat[criteria]) ? 1 :
			stat[criteria] + 1;
		return stat;

cyclejs-audio-driver.js

GitHub: jemmyw/cyclejs-audio-driver

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* @param {Function} setter
* @return {Lens}
* @see R.view, R.set, R.over, R.lensIndex, R.lensProp
* @example
*
*      var xLens = R.lens(R.prop('x'), R.assoc('x'));
*
*      R.view(xLens, {x: 1, y: 2});            //=> 1
*      R.set(xLens, 4, {x: 1, y: 2});          //=> {x: 4, y: 2}
*      R.over(xLens, R.negate, {x: 1, y: 2});  //=> {x: -1, y: 2}

+ 17 other calls in file

Ai Example

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const { lens, prop, assoc } = require("ramda");

const myLens = lens(prop("myProperty"), assoc("myProperty"));

const myObject = { myProperty: "hello" };

console.log(myLens.get(myObject)); // Output: 'hello'

const updatedObject = myLens.set(myObject, "world");

console.log(updatedObject); // Output: { myProperty: 'world' }

In this example, we create a lens using ramda.lens that focuses on the myProperty property of an object. We use the prop and assoc functions to create the getter and setter functions for the lens, respectively. We then use the get method of the lens to retrieve the value of the myProperty property of an object, and the set method of the lens to update the value of the myProperty property of an object.

xs.js

GitHub: octachrome/t2

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  // Context -> Player
  const getter = context => context.players[context.whoseTurn];
  // Context -> Player -> Context
  const setter = (player, context) => R.evolve({players: R.update(context.whoseTurn, player)}, context);


  return R.lens(getter, setter);
})();


const processing = lens => m => State.get().chain(s0 => {
  const [res, s1] = m.runWith(R.view(lens, s0)).toArray();

+ 13 other calls in file

monad.js

GitHub: octachrome/t2

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randomTurnS2 = processingFst(randomInputS).chain(inp =>
    processingSnd(turnS(inp)));
console.log(mapM(_ => randomTurnS2, R.range(0, 6)).runWith(Pair(mkStdGen(51), TurnState.Locked)));


fstL = R.lens(fst, (value, pair) => pair.bimap(R.always(value), R.identity));
sndL = R.lens(snd, (value, pair) => pair.bimap(R.identity, R.always(value)));


const processing = (lens, m) => State.get().chain(s0 => {
    const [res, s1] = m.runWith(R.view(lens, s0)).toArray();
    return State.put(R.set(lens, s1, s0)).map(() => res);

+ 9 other calls in file

bundle.js

GitHub: Gaoey/canvas-vertice-google-detected-text

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* @param {Function} setter
* @return {Lens}
* @see R.view, R.set, R.over, R.lensIndex, R.lensProp
* @example
*
*      const xLens = R.lens(R.prop('x'), R.assoc('x'));
*
*      R.view(xLens, {x: 1, y: 2});            //=> 1
*      R.set(xLens, 4, {x: 1, y: 2});          //=> {x: 4, y: 2}
*      R.over(xLens, R.negate, {x: 1, y: 2});  //=> {x: -1, y: 2}

+ 3 other calls in file

t2.js

GitHub: octachrome/t2

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  // Game -> Player
  const getActivePlayer = game => game.players[game.whoseTurn];
  // Game -> Player -> Game
  const setActivePlayer = (player, game) => R.evolve({players: R.update(game.whoseTurn, player)}, game);


  return R.lens(getActivePlayer, setActivePlayer);
})();


const Player = {};

+ 3 other calls in file

flens.cjs.js

GitHub: acwhittam/flens

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    ramda.chain(([v, t]) => toFuture(ramda.set(l, v, t))),
    fluture.both(toFuture(value))
)(toFuture(target)));




const wrap = (l) => ramda.lens(
    getter(l),
    setter(l)
);

index.js

GitHub: VesaLahd/aoc2022

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const fs = require('fs')
const R = require('ramda')


const content = R.split('\n', fs.readFileSync(`${__dirname}/input.txt`, {encoding: 'utf-8'}))


const lastLens = R.lens(a => a[R.dec(R.length(a))],
  R.curry((v, a) => R.set(R.lensIndex(R.dec(R.length(a))), v, a)));


const directionToVector = R.cond([
  [R.equals('U'), R.always([0, 1])],

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