Persistent functional object updates on vanilla js data structures (wraps react-addons-update)
import{updateIn,merge,push,unshift,splice,assoc,dissoc}from'update-in';constval={a: {b: 0,c: 2},xs: [1,2]};updateIn(val,['a','b'],v=>v+1)// => {a: {b: 1, c: 2}, xs: [1, 2]}updateIn(val,['a','b'],v=>v+10)// => {a: {b: 10, c: 2}, xs: [1, 2]}letadd=(...args)=>args.reduce((a,b)=>a+b,0);updateIn(val,['a','b'],add,1,2,3)// => {a: {b: 6, c: 2}, xs: [1, 2]}updateIn(val,['a','b'],v=>99)// => {a: {b: 99, c: 2}, xs: [1, 2]}merge({x: 1,y: 1},{y: 2,z: 2})// => {x: 1, y: 2, z: 2}updateIn(val,['a'],merge,{c:99,d: 99})// => {a: {b: 0, c: 99, d: 99}, xs: [1, 2]}updateIn(val,['xs'],push,[3])// => {a: {b: 0, c: 2}, xs: [1, 2, 3]}updateIn(val,['xs'],push,[99])// => {a: {b: 0, c: 2}, xs: [1, 2, 99]}updateIn(val,['xs'],unshift,[0])// => {a: {b: 0, c: 2}, xs: [0, 1, 2]}updateIn(val,['xs'],splice,[[1,1,20]])// => {a: {b: 0, c: 2}, xs: [1, 20]}updateIn(val,['xs'],splice,[[0,1,6,5],[4,0,99,99]])// => {a: {b: 0, c: 99, d: 99}, xs: [6,5,2,99,99]}updateIn(val,['a'],assoc,'b',1);// => {b: 1, c: 2}updateIn(val,['a'],assoc,'b',5,'c',6);// => {b: 5, c: 6}updateIn(val,['a'],assoc,'d',4);// => {b: 0, c: 2, d: 4}updateIn(val,['a'],assoc,'d',4,'e',6);// => {b: 0, c: 2, d: 4, e: 6}updateIn(val,['a'],assoc,'d',4,'e')// => Error('assoc expects an even number of arguments')updateIn(val,['xs'],assoc,0,3);// => [3, 2]updateIn(val,['xs'],assoc,0,3,1,4);// => [3, 4]updateIn(val,['xs'],assoc,2,3);// => [1, 2, 3]updateIn(val,['xs'],assoc,1,false,0)// => Error('assoc expects an even number of arguments')updateIn(val,['xs'],assoc,1.5,'not an int')// => TypeError('assoc expects only integer keys')updateIn(val,['xs'],assoc,-1,'negative index?')// => RangeError('assoc expects only numeric keys in the range [0, array.length]')updateIn(val,['xs'],assoc,3,'sparse arrays?')// => RangeError('assoc expects only numeric keys in the range [0, array.length]')constcollections={object: {foo: 1,bar: 2,baz: 3},array: [1,2,3,4,5,6,7]};updateIn(collections,['object'],dissoc,'bar')// => {foo: 1, baz: 3}updateIn(collections,['object'],dissoc,'foo','baz')// => {bar: 2}updateIn(collections,['array'],dissoc,1)// => [1, 3, 4, 5, 6, 7]updateIn(collections,['array'],dissoc,2,3,4)// => [1, 2, 6, 7]updateIn(collections,['array'],dissoc,1,3,5)// => [1, 3, 5, 7]These combinators use structure sharing to preserve === for unchanged nodes, structure sharing is provided by react-addons-update. As of React 0.14, react-addons-update requires all of React as a peer dependency.
We can implement cursors in very few lines with updateIn, see the examples subdirectory.