Here’s an attempt:
var readOnlyLength = $('#field').val().length;
$('#output').text(readOnlyLength);
$('#field').on('keypress, keydown', function(event) {
var $field = $(this);
$('#output').text(event.which + '-' + this.selectionStart);
if ((event.which != 37 && (event.which != 39)) &&
((this.selectionStart < readOnlyLength) ||
((this.selectionStart == readOnlyLength) && (event.which == 8)))) {
return false;
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script>
<input id="field" type="text" value="CAN'T TOUCH THIS!" size="50" />
<div id="output">
</div>
This disables keys other than the left and right arrows for the read-only part. It also disables the backspace key when just at the end of the read-only part.
From what I’ve read, this won’t work on IE <= 8.
Here it is in plain JavaScript (no JQuery):
function makeInitialTextReadOnly(input) {
var readOnlyLength = input.value.length;
field.addEventListener('keydown', function(event) {
var which = event.which;
if (((which == 8) && (input.selectionStart <= readOnlyLength)) ||
((which == 46) && (input.selectionStart < readOnlyLength))) {
event.preventDefault();
}
});
field.addEventListener('keypress', function(event) {
var which = event.which;
if ((event.which != 0) && (input.selectionStart < readOnlyLength)) {
event.preventDefault();
}
});
}
makeInitialTextReadOnly(document.getElementById('field'));
<input id="field" type="text" value="CAN'T TOUCH THIS!" size="50" />