dojo.setContext¶
| since: | V? |
|---|
Contents
Changes the behavior of many core Dojo functions that deal with namespace and DOM lookup.
Introduction¶
“dojo.setContext” allows many of Dojo’s core functions to easily switch context (e.g. from the current window to an iframe) with a single function call.
For example, dojo.query references the “window” global variable when performing searches by default.
[ Dojo 1.7 AMD ]
require(["dojo/query"], function(query){
var dojoLinks = query('a');
var nativeLinks = document.getElementsByTagName('a');
// Returns true, as they're searching the same window.document
console.log(dojoLinks.length === nativeLinks.length);
});
[ Dojo < 1.7 ]
var dojoLinks = dojo.query('a');
var nativeLinks = document.getElementsByTagName('a');
// Returns true, as they're searching the same window.document
console.log(dojoLinks.length === nativeLinks.length);
This is because dojo stores many of the common global variables:
| window: | dojo.global |
|---|---|
| document: | dojo.doc |
| body: | dojo.body() |
By calling “dojo.setContext” (which modifies the convenience variables above), you can easily query another frame’s content.
Usage¶
Dojo 1.7 (AMD)¶
require(["dojo/_base/window"], function(win){
win.setContext(window, window.document);
// or
win.setContext(myIframe.contentWindow, myIframe.contentWindow.document);
});
Dojo < 1.7¶
dojo.setContext(window, window.document);
// or
dojo.setContext(myIframe.contentWindow, myIframe.contentWindow.document);
Examples¶
Counting Links¶
Here is a simple example that counts the links in the current page as well as the links in an embedded iframe, via dojo.setContext.
HTML¶
<a href="#">I'm the only link on this page!</a>
Number of links on this page:
<input type="text" name="these_links" value="" id="these_links">
<br />
Number of links in the iframe:
<input type="text" name="those_links" value="" id="those_links">
<br />
<!-- We have to count the links AFTER the iframe has loaded -->
<iframe src="resources/links.html" id="iframe" onload="countLinks();"></iframe>
JavaScript¶
[ Dojo 1.7 AMD ]
require(["dojo/dom", "dojo/query", "dojo/_base/window"], function(dom, query, win){
var countLinks = function(){
var these = dom.byId('these_links');
var those = dom.byId('those_links');
var iframe = dom.byId('iframe').contentWindow;
// Count the number of links in *this* page
these.value = query('a').length;
// Change context from current window to iframe
win.setContext(iframe.window, iframe.window.document);
// Count the number of links in the *iframe*
those.value = query('a').length;
};
});
[ Dojo < 1.7 ]
var countLinks = function(){
var these = dojo.byId('these_links');
var those = dojo.byId('those_links');
var iframe = dojo.byId('iframe').contentWindow;
// Count the number of links in *this* page
these.value = dojo.query('a').length;
// Change context from current window to iframe
dojo.setContext(iframe.window, iframe.window.document);
// Count the number of links in the *iframe*
those.value = dojo.query('a').length;
};