替换数组中的元素

Question

What is a clean way to replace elements in an array in ES2019?

This is my code, but it iterates the array multiple times:

function findReplace(item, target, replacement){
  return item === target ? replacement : item
}

const a = [1,2,3,4,5,5,4,3,2,1]
console.log(a.map(item => findReplace(item, 1, 10))
             .map(item => findReplace(item, 2, 20)))
//[10,20,3,4,5,5,4,3,20,10]

Answer 1

Create a map for the translation:

 const a = [1,2,3,4,5,5,4,3,2,1] const map = new Map([[1, 10], [2, 20]]); console.log(a.map(item => map.get(item)??item)) //[10,20,3,4,5,5,4,3,20,10]

If you want to replace values with null or even undefined , then the ?? operator is not the right tool. In that case:

 const a = [1,2,3,4,5,5,4,3,2,1] const map = new Map([[1, null], [2, undefined], [3, 33]]); console.log(a.map(item => map.has(item)? map.get(item): item))

Answer 2

Another way is to use object called mapping .

 const a = [1,2,3,4,5,5,4,3,2,1] const mapping = {1: 10, 2: 20}; const result = a.map(v => mapping[v] || v); console.log(result)