I was busy making a JavaScript code that allows me to make GUI page elements to have custom context menus, when I thought about checking to see if an element exists in order to make a context menu for it.
function element_exists(el){
var tagName=el.tagName;
var exists=0;
for(var a=0;a<document.getElementsByTagName(tagName).length;a++){
if(document.getElementsByTagName(tagName)[a]==el){
exists=1;
}
}
return exists;
}
In this code, I pass a reference to a DOM element object (which is stored from earlier).
Let's say that it was stored, but since then I removed the element itself from the document.
I'm using Chrome Canary, and even if I edit the page through the console and make a new element with the exact same tag name and ID, it returns false. Would it return true if it had the same innerText and innerHTML?
If not, is this a standard in all web browsers (old and new)?
Just curious because I could eliminate some unnecessary code if they're all unique.
I'm pretty sure the answer is no; each element is unique, regardless of whether they have similar values (including "id").
This might provide you some insight into how element garbage collection works in Chrome. I'm not sure how the other browsers respond though.
http://www.html5rocks.com/en/tutorials/memory/effectivemanagement/
It outlines some tools that might be useful to test your theory.
Related
The functionality I seek is very similar to the default ModelStructurePanel model browser, except that I need to list only a subset of elements, by passing a list of dbIds of the elements I want listed. By clicking on an element on that list, have the view focus on that element.
I figure there might be two ways of achieving this by using the ModelStructurePanel (although I'm open to using something else):
Creating a new instanceTree with only the specified elements, then doing something like viewer.modelstructure.setModel(newInstanceTree)
Overwriting the ModelStructurePanel.shouldInclude method to hide all elements but the specified ones.
I have googled for Viewer code boilerplate that would provide this functionality, but have not found it. Any help is very much appreciated.
There is a basic sample here very close to what you described, and I would go with customizing just one action instead create a new one, seems easier.
Here is the website I am trying to access. I dont want the default tab (Day) though, I want to select the Season tab
https://www.eex.com/en/market-data/power/futures/uk-financial-futures#!/2017/05/23
The link appears to be exactly the same whichever tab is chose making differentiation impossible as far as I can tell.
Any help on this would be much appreciated, using whichever programming method and language is appropriate.
Kind Regards
Barry Walsh
The URL does not change since this is an ajax request, which you can see from MarketDataTableAController's getPageData function. You can read about them here https://developer.mozilla.org/en-US/docs/AJAX/Getting_Started
Ive inspected your html and you seem to be using angular. On further inpection you can see that the tabs have ng-click="setActiveTab(tab)" attribute on them. So whenever user clicks, this function gets executed. It is a matter of using this function with the appropriate tab object to get the content to change. You for example could put setActiveTab(tab) into your controller init method since setActiveTab() calls the forementioned getPageData() function to update the page.
Also the tab you are looking for is page.tabs[5] ($parent.page.tabs[5] if referring from TabController) since this is the tab with the label of season. Pass that to setActiveTab() and it should show you the season instead.
However this might not be a good solution since the tab array ordering might change. Then you would need to loop over all objects in page.tabs and see if tab.label === "Season" and pass that in the function instead or better yet use the $filter service provided by angular which would look more cleaner.
Your code source also seems to be minimized and its not very easy to read.
I'm a bit of trouble instantiating a custom template, and making all the bindings work. My custom element which has to do this is quite similar to polymer/core-list, with a few differences. Like core-list, the parent adds the element invokes my custom element, and adds a template as its content, as seen here.
Unlike core-list, the element adds an id to this template, and creates a few templates which refer to that one, as seen here. Finally, when the time comes, these new templates are used to create a few elements and add them in the dom.
That's all fine and good, and mostly, it works correctly. The model data is used to fill the resulting element correctly, and the default filters work, thanks to the PolymerExpressions used as a bindingDelegate. However, event handlers do not seem to work.
I don't know whether the handler function can't be found in whatever scope is used, or something else is at play here. The only thing I currently know is that the on-tap attribute value is empty when I look at the polymer-icon-button through the web inspector. With a very similar usage using the core-list, the event handler works. The web inspector there shows the polymer expression as the value of the on-tap attribute. And both handlers are defined in the parent element which contains the invokations of core-list and my element, and the templates which are passed to the corresponding contents.
I'm using Delphi 2009 and I want to find index of HTML table which contains given element.
So, in the application, which I created, I use web browser to see the web page. I want to select element from this page and want to get Index of table which contains this element.
If someone can do it, please help me
Using the browser's DOM interfaces, locate the IHTMLElement interface of the desired HTML element as needed, then use its parentElement property to get its parent element, repeating as needed, until you find an element that supports the IHTMLTableCell interface. Its cellIndex property will tell you the index of the cell within its row. Keep iterating the parentElement chain until you find an element that supports the IHTMLTableRow interface. Its rowIndex property will tell you the index of the row within its table. If you need to access the table itself, keep iterating the parentElement chain until you find an element that supports the IHTMLTable interface.
I have a web application for tagging data and viewing data by tag, so my UI is a list of checkboxes for each tag, a list of checkboxes for each data item, a "Tag" button, which adds the checked tags to the checked data, and a "Filter" button, which ignores the checked data and just displays only the data items with the given tag.
My problem is that the former operation (tagging data) is "obviously" a POST operation, whereas the latter operation (viewing data according to a tag) is "obviously" a GET operation. But the method attribute is attached to the form, not the submit button, so I have to choose one or other for both buttons.
I don't want to make two forms, since as far as I can tell this would force me to duplicate the entire tag list. Is there any way I can choose my method based on the choice of submit button?
A JavaScript solution is permissible, but one without would be preferred.
(I am going to post an answer to this question, but I don't particularly like it, so I would welcome alternatives).
In principle, you could use the formmethod attribute in a submit button, as per HTML5. However, it is not recognized by IE, even in IE 9. The existence of the feature in HTML5 indirectly proves that previous versions of HTML lack a feature for this.
On the other hand, the POST method can be used even for simple viewing that does not cause any changes in the outside world, and in many situations it has to be used for technical reasons (e.g., too much data). So I think the method issue is not very relevant; just use POST.
I would honestly go with a javascript solution, in the onsubmit of the form fire a method which a) checks the submit button that was pressed and b) based on this changes the method of the form.
One possible solution would be to use POST, and then have the server give a 303 See Other header to change it into a GET request. This involves making two requests to serve the purpose of one, which is unfortunate, but at least means that the URL will change so people can link to a specific tag selection.
I agree with javascript solution, proposed by Jon Taylor, the problem is not if your form's method is GET or POST, but how do you filter/validate/sanitize user input. If your concern is related to the fact, that the user can manipulate the form's method, then you should implement solution to that matter on server side.