JSFiddle - React, Tailwind, and code Playground

by Mi_Creativity

HTML

<select id="slct">
    <option></option>
    <option value="1">id 1</option>
    <option value="2">id 2</option>
    <option value="3">id 3</option>
    <option value="4">id 4</option>
</select>
<input type="text" id="un" disabled>
<input type="text" id="dob" disabled>

JavaScript

var $select = document.getElementById('slct'),
    $un = document.getElementById('un'),
    $dob = document.getElementById('dob'),
    val, arr, username, dob;

// usually this array is obtained from a server response 
arr = [
    	usr1 = ['user1', 'dob1'],
    	usr2 = ['user2', 'dob2'],
    	usr3 = ['user3', 'dob3'],
    	usr4 = ['user4', 'dob4']
    ];

$select.addEventListener('change', function(){
	val = this.value - 1; // because arrays start at 0.
	username = arr[val][0];
    dob = arr[val][1];
    $un.value = username;
    $dob.value = dob;
});