remove item from array in a declarative way, avoiding array mutations

removeItemFromArray.js

/* 
  remove item from array in a declarative way, 
  avoiding array mutations 
  
  Instead of splicing
*/

// 1. use Array.filter

const removeItem = (list,index) => list.filter((item,i) => index !== i)

removeItem( [0,10,20], 1)

// => [0, 20]

// 2. use Array.slice

const removeItem = (list,index) => list.slice(0,index).concat(list.slice(index+1)); 
    // (copy the previous and next parts of the index into a new array)
//using ...array spread es6
const removeItem = (list,index) => [ ...list.slice(0,index), ...list.slice(index+1) ]; 


removeItem( [0,10,20], 1)

// => [0, 20]