jquery - How can I add an unremovable prefix to an HTML input field?

Question

Using jQuery, how can I add a default value of http:// into an input field that can’t be removed, but that still allows you to type a URL after it?

Default: http://
Url: http://www.domain.name

Answer 1

this works well for me:

$("input").keydown(function(e) {
var oldvalue=$(this).val();
var field=this;
setTimeout(function () {
    if(field.value.indexOf('http://') !== 0) {
        $(field).val(oldvalue);
    } 
}, 1);
});

http://jsfiddle.net/J2BKU/