A Touch of Technology

Writings from Alex

Scope jQuery Selection

Wednesday February 17, 2016

Warning: You probably shouldn’t be using jQuery any more, this is an old article. Please tread with caution when referencing this article.

Here is a simple and effective way to pass different jQuery contexts around for manipulation in client packages. Recently I was presented with the issue of instantiating multiple iframes within a single page, all of which would have a small package loaded inside them to run and manipulate itself. These packaged units needed a handle on their own iframe as well as the parent document.

$ is setup to work off the current document. When no context is provided to the jQuery() selector method then the context of document is used. I could have manipulated the selector or used other jQuery helper methods to get a handle on the parent document, but that would get messy very fast and could make the packaged code difficult to read.

A cleaner solution is to have two seperate selector handles, one on the unit iframe document and one on the top.document. This approach can be used to limit the selector for anything but for my case I needed top.document.

import $unit from 'jquery'
import $top from 'utils/jquery-top'

In the above example jquery is just the defacto jquery installed as a dependency via npm. The second import statement is a custom abstraction to the defacto jquery library which allows me to override the seletor method and limit the context to top.document.

import jQuery from 'jquery'

let bling = function(selector, context = top.document) {
  return new jQuery.fn.init(selector, context)
bling.fn = bling.prototype = jQuery.fn
jQuery.extend(bling, jQuery)

export default bling

Now when I’m in the unit packaged code I can have a handle on both the top.document as well as the individual unit iframe document.

$unit('.content-body').text('This is an example')

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