Initially, updating select elements in this manner may not be the most efficient approach. Are you planning to use them interactively later on? Selecting an option and triggering a corresponding action in the browser may not work as expected if you simply insert options directly into the select element's body. Furthermore, some browsers may not recognize these options as functional.
To dynamically change the select options, it is recommended to manipulate the select element's `options` collection like so:
var new_options = {4: "Four", 5: "Five", 6: "Six"}; // or fetched from an Ajax callback
var options_two = $('options_two'); // reference the select element
options_two.options.length = 0; // clear existing options
for(var i in new_options){
// utilize new Option() constructor to create new option for each value/label pair
options_two.options[options_two.options.length] = new Option(new_options[i], i);
};
This method ensures that any attached observers will continue to function properly and maintains continuity in how the form is processed by the browser.
Secondly, Ajax.Updater simplifies the combination of Ajax.Request() and Element.update(). It can be visualized like this:
new Ajax.Request('your/endpoint', {
onComplete: function(transport){
$('your_element').update(transport.responseText);
}
});
To incorporate Ajax.Updater into your code, enclose both select tags within a shared parent container and ensure that the server response includes fully constructed select tags. However, bear in mind that existing callbacks on the page would lose reference to the original select tags after being replaced. Thus, new listeners must be attached to manage the replacements effectively to prevent memory leaks.
In one recent project I worked on, I integrated these concepts as follows:
document.on('click', 'input.team', function(evt, elm){
if($('project_project_template_id')){
var picker = $('project_project_template_id').enable();
var team = $$('input.team:checked').first();
new Ajax.Request('/teams/' + $F(team) + '/project_templates.json', {
onSuccess: function(xhr){
var opts = xhr.responseJSON;
picker.options.length = 0;
opts.each(function(o){
picker.options[picker.options.length] = new Option(o['name'], o['id']);
});
}
});
}
});
In case you need to update multiple pickers, nest them in your JSON response structure, like the following example returned from the server:
{"options_one": {4: "Four", 5: "Five"}, "options_two": {6: "Six", 7: "Seven"}}
By structuring your JSON response accordingly, you can update multiple pickers with a single Ajax request.