How do I insert a character at the caret with javascript?

Question

I want to insert some special characters at the caret inside textboxes using javascript on a button. How can this be done?

The script needs to find the active textbo

Answer 1

In light of your update:

var inputs = document.getElementsByTagName('input');
var lastTextBox = null;

for(var i = 0; i < inputs.length; i++)
{
  if(inputs[i].getAttribute('type') == 'text')
  {
    inputs[i].onfocus = function() {
      lastTextBox = this;
    }
  }
}

var button = document.getElementById("YOURBUTTONID");
button.onclick = function() {
  lastTextBox.value += 'PUTYOURTEXTHERE';
}