Hola
Sería algo así
Código Javascript
:
Ver originalvar ulIndex = false;
function funcion(sel) {
var contSel = 0;
for (var i = 0; i < sel.options.length; i++) {
if (sel.options[i].selected == true) {
contSel++;
}
}
if (parseInt(contSel) > 2) {
alert('has superado el máximo');
sel.options[ulIndex].selected = false;
}
}
Código HTML:
Ver original<select multiple="multiple" size="4" id="elSel" onchange="funcion(this)"> <option value="val" onmousedown="ulIndex = this.index">val
</option> <option value="val" onmousedown="ulIndex = this.index">val
</option> <option value="val" onmousedown="ulIndex = this.index">val
</option> <option value="val" onmousedown="ulIndex = this.index">val
</option> <option value="val" onmousedown="ulIndex = this.index">val
</option>
Suerte