JSFiddle - React, Tailwind, and code Playground

JavaScript

let state = {
  title: [{
    title: 'Welcome',
    feature: 'test'
  }]
}

function setState(state) {
  return Object.assign({}, state.title[0], { title: 'a' });
}

console.log(setState(state))

//state = Object.assign({}, state.title[0], { title: 'a' });
//console.log(state)