JSFiddle - React, Tailwind, and code Playground

JavaScript

var users = [
  {
    firstname : "jetlag",
    lastname: "son"
  },
  {
    firstname : "becky",
    lastname: "love"
  },
  { 
    firstname : "just",
    lastname: "me"
  }
];

function matchName(name) {
  for (var i = 0; i < users.length; i++) {
      if(users[i].firstname == name) {
          return users[i];
      } else {
          console.log('user does not exist')
      }
  }
}

console.log(matchName("jetlag"));