用JS展开select的下拉框

[mishe]

function showallselect(id){
    var select = document.getElementById(id);
    if(select && select.options && select.options.length >1){
        select.size = select.options.length;
    }
}
···

[mishe]

唤起select的option展开

zepto方式:

$(sltElement).trrgger("mousedown");
原生js方式:

function showDropdown(sltElement) {
var event;
event = document.createEvent('MouseEvents');
event.initMouseEvent('mousedown', true, true, window);
sltElement.dispatchEvent(event);
};