How to know google map controls creation is done? - google-maps

Question

I need to dynamically create a ui widget with a parent div.id='myDivId', which is a google map control.
var centerControlDiv = document.createElement('div');
var centerControl = new CenterControl(centerControlDiv, map);
centerControlDiv.index = 1;
centerControlDiv.id = 'myDivId';
map.controls[google.maps.ControlPosition.TOP_CENTER].push(centerControlDiv);
// $('#myDivId') causes exception as $('#myDivId') is not created on
// map as a DOM element yet.
var uiWidget = new uiWidget('myDivId');
// $(#myDivId) is used in class uiWidget().
class uiWidget {
constructor(divId) {
this.id = divId;
// It should fail here due to this.$div property, as
// div 'myDivId' is not a DOM element yet by google map
// controls API.
this.$div.click($.proxy(this.event_click, this));
}
get $div() {
return $(‘#’ + this.id);
}
event_click(eve) {
}
}
But, there is no event of when this parent div is created. Therefore, the child ui widget can't be created at correct time.
How to know parent div with id 'myDivId' is created?

Answer 1

You are trying to reference a DOM element by ID as a child of document when that element has only been created but not yet added to the document.
But you already have a reference to the #myDivId element in the centerControlDiv variable, so you don't need to use the ID to reference it. Just change this line:
$('#myDivId').append("<div>UI widget</div>");
to:
$(centerControlDiv).append("<div>UI widget</div>");
Put another way, to answer your question "How to know parent div with id 'myDivId' is created?", that div already is created - you created it in the document.createElement('div') call. It just isn't a child of document yet.
So when you use $('#myDivId'), or similar calls like document.getElementById('myDivId'), those calls can't see it. It's just a standalone element that you have a reference to, so you can access it through that element instead of looking it up in the document DOM.
Update based on your latest code:
To apply this principle to your uiWidget class, you can have the class work with the actual div element you created instead of accessing it by ID. Even better, since you're using jQuery, pass it a jQuery object from the beginning, like this:
var uiWidget = new UiWidget( $(centerControlDiv) );
class UiWidget {
constructor($div) {
this.$div = $div;
this.$div.click($.proxy(this.event_click, this));
}
// ...
}
As you can see, the code no longer requires the div ID at all, and it doesn't need the get $div() either. $div and this.$div are already a jQuery object wrapping your centerControlDiv.
I also changed the name of the class to UiWidget to follow recommended JavaScript style and avoid conflict with the uiWidget variable that holds an instance of the class.