JSFiddle - React, Tailwind, and code Playground

JavaScript

var a =[
   {
      title: 'Title 1',
      value: 'value 1'
   },
   {
      title: 'Title 2',
      value: 'value 2'
   }
]
a.forEach(function(item,index){
item.newParam=index

});
console.log(a)