Array

Immutable operations (Add,remove, update) in a array

  const number = [1,2,3];

  // add at the end
  const addedAtEnd = [...number,4];
  
  // add in between
  const index = number.indexOf(2);
  const addedInBetween = [
    ...number.slice(0,index),
    4,
    ...number.slice(index),
  ];
  
  // add at the beginning
  const addedAtBegin = [ 4 , ...number ];
  
  // removing an element
  const removed = number.filter(n => n !==2);
  
  //update an element
  const updated = number.map(n=>(n === 2 ? 20 : n));
  

Famous libraries for immutability

• immutable

  import {Map} from "immutable";
  
  let book = Map({title: "wings of fire"});
  
  function publish(book){
    return book.set("isPublish", true);
  }
  
  book = publish(book);
  
  console.log(book.toJs());  

• (immer)[https://immerjs.github.io/immer/docs/introduction]

  import {produce} from "immer";
  
  let book = Map({title: "wings of fire"});
  
  function publish(book){
    return produce(book, (draft) => {
      draft.isPublish = true;
    });
  }
  
  let updated = publish(book);
  
  console.log(book);  
  console.log(updated);  

• mori