wiki/client/js/helpers/form.js

function setInputSelection(input, startPos, endPos) {
    input.focus();
    if (typeof input.selectionStart != "undefined") {
        input.selectionStart = startPos;
        input.selectionEnd = endPos;
    } else if (document.selection && document.selection.createRange) {
        // IE branch
        input.select();
        var range = document.selection.createRange();
        range.collapse(true);
        range.moveEnd("character", endPos);
        range.moveStart("character", startPos);
        range.select();
    }
}