Disable fields

stackoverflow

by Neviton

HTML

<input type="text" name="name1" id="name1" placeholder="Name 1"/>
<input type="text" name="name2"id="name2" placeholder="Name 2"/>

JavaScript

var name1 = document.getElementById('name1'),
		name2 =document.getElementById('name2');
    
name1.onkeyup = function(e) {
	if (name1.value.length > 0) {
  	name2.setAttribute('disabled', 'disabled');
  } else {
  	name2.removeAttribute('disabled');
  }
}

name2.onkeyup = function(e) {
	if (name2.value.length > 0) {
  	name1.setAttribute('disabled', 'disabled');
  } else {
  	name1.removeAttribute('disabled');
  }
}