Error using built version of Dojo (but not the uncompressed source) - javascript

I noticed something weird when using the uncompressed source of Dojo our code runs normally without error. I tried these two from the archives so far
dojo-release-1.10.6-src and dojo-release-1.10.8-src
However when I switch to the built versions, either
dojo-release-1.10.6 or dojo-release-1.10.8
There is an error that occurs when using dojo.query
TypeError: root.getElementsByTagName is not a function
My function call looks like this
var dom_frag = domConstruct.toDom(response);
var title = dojo.query(".accordion_title", dom_frag)[0];
where response contains HTML string. (too long to post here)
EDIT: Image of debugger showing contents of 'dom_frag'

Ok, have you checked to see if the dom_frag variable is a single dom node? If the dom fragment is multiple nodes, then the dojo.query won't work, because it needs to search the children of a single dom node.
To solve this, try wrapping the toDom contents with a single node... like so:
var dom_frag = domConstruct.toDom("<div>"+response+"</div>");
var title = dojo.query(".accordion_title", dom_frag)[0];
This is, of course, a bit of a hack... but if you can't guarantee that the response will end up a single node, then you need to do it.

Make sure your root is actually a DOM element as:
the Element.getElementsByTagName() method returns a live
HTMLCollection of elements with the given tag name. The subtree
underneath the specified element is searched, excluding the element
itself. Ref.

Related

href attribute set, javascript sees as empty string

I am experiencing odd behaviour in Chrome (v43.0.2357.134) whereby I am reading an anchor element's .href attribute, but in specific circumstances its value is an empty string.
I would like the .href value to be populated on all anchors.
Issue
Specifically, this is what is being observed:
//Bad (unwanted) behaviour
var currentElem = ; //Code to pick out an anchor element
console.info(currentElem.href); //"" (empty string)
console.info(currentElem.getAttribute('href'); //"path/to/other/page.html"
Edited to add/clarify: Note that in this screenshot, at the point of reaching the fourth line of code the value of nextPageUri is an empty string (otherwise would not have reached the debugger; line). The fifth line then populates nextPageUri with the .getAttribute('href') value, hence the value showing next to line two.
This is what is (correctly) seen within Firefox, and on the first TWO DOMs via Chrome:
//Good (desired) behaviour
var currentElem = ; //Code to pick out an anchor element
console.info(currentElem.href); //"http://example.org/root/dir/path/to/other/page.html"
console.info(currentElem.getAttribute('href'); //"path/to/other/page.html"
Background
Context: This is within a script to inline multiple pages of search results to a single page, and the anchor elements are located within a DOM retrieved via xmlHttpRequest. The code runs perfectly via Firefox for >100 pages.
Confusingly, the incorrect behaviour described above only occurs on the third and subsequent requests in the Chrome browser.
This is an issue with Chromium/Blink-based browsers: if you use DOMParser to parse string into a document, href properties with relative URI (i.e. doesn't start with http[s]) will be parsed as empty string.
To quote tkent from Chromium issue 291791:
That's because a document created by DOMParser doesn't have baseURI. Without baseURI, relative URI references are assumed as invalid.
Same thing happens if you use createHTMLDocument. (Chromium issue 568886)
Also, based on this test code posted by scarfacedeb on Github, src properties also exhibit the same behavior with relative URIs.
As you have pointed out, using getAttribute() instead of the dot notation works fine.
Chrome's "element.href" doesn't act any differently on the 3rd try than it does on the first 2 -- you mentioned that you are paginating, when this error happens. how does the "href" attribute on the Next Page link get set each time you arrive at the page? It seems likely that your code to evaluate the element's href attribute is simply running before the href is set -- as evidenced by your debugger being able to evaluate it after a pause.
Try and reproduce this issue in a plunkr.
I know you're checking if nextPageUri is empty.
But, could you try always using
nextPageUri = currentElem.getAttribute('href');
and see if that works?
I experienced a similar problem using a DOMParser for translating text/html pages coming from ajax requests and, after that, finding href's of <a> elements inside it.
For instructions purpose, this is how I'm using the parser
var parser = new DOMParser();
$.ajax({....}).done(function(request){
var page = parser.parseFromString(request, 'text/html');
});
Test yourself
If you want to test the behaviour of .href and .getAttribute("href") yourself, please run this code at chrome dev tools console:
parser = new DOMParser(); // create your DOMParser
// the next line creates a "document" element with an <a> tag inside it
parsed_page = parser.parseFromString('click here', 'text/html');
link = parsed_page.getElementsByTagName('a')[0]; // locate your <a> tag
link.href; // this line returns ""
link.getAttribute('href'); // this line returns "test"

using document.createDocumentFragment() and innerHTML to manipulate a DOM

I'm creating a document fragment as follow:
var aWholeHTMLDocument = '<!doctype html> <html><head></head><body><h1>hello world</h1></body></html>';
var frag = document.createDocumentFragment();
frag.innerHTML = aWholeHTMLDocument;
The variable aWholeHTMLDocument contains a long string that is the entire html document of a page, and I want to insert it inside my fragment in order to generate and manipulate the DOM dynamically.
My question is, once I have added that string to frag.innerHTML, shouldn't it load this string and convert it to a DOM object?
After setting innerHTML, shouldn't I have access to the DOM through a property?
I tried frag.childNodes but it doesn't seem to contain anything, and all I want is to just access that newly created DOM.
While DocumentFragment does not support innerHTML, <template> does.
The content property of a <template> element is a DocumentFragment so it behaves the same way. For example, you can do:
var tpl = document.createElement('template');
tpl.innerHTML = '<tr><td>Hello</td><td>world</td></tr>';
document.querySelector('table').appendChild(tpl.content);
The above example is important because you could not do this with innerHTML and e.g. a <div>, because a <div> does not allow <tr> elements as children.
NOTE: A DocumentFragment will still strip the <head> and <body> tags, so it won't do what you want either. You really need to create a whole new Document.
You can't set the innerHTML of a document fragment like you would do with a normal node, that's the problem. Adding a standard div and setting the innerHTML of that is the common solution.
DocumentFragment inherits from Node, but not from Element that contains the .innerHTML property.
In your case I would use the <template> tag. In inherits from Element and it has a nifty HTMLTemplateElement.content property that gives you a DocumentFragment.
Here's a simple helpermethod you could use:
export default function StringToFragment(string) {
var renderer = document.createElement('template');
renderer.innerHTML = string;
return renderer.content;
}
I know this question is old, but I ran into the same issue while playing with a document fragment because I didn't realize that I had to append a div to it and use the div's innerHTML to load strings of HTML in and get DOM Elements from it. I've got other answers on how to do this sort of thing, better suited for whole documents.
In firefox (23.0.1) it appears that setting the innerHTML property of the document fragment doesn't automatically generate the elements. It is only after appending the fragment to the document that the elements are created.
To create a whole document use the document.implementation methods if they're supported. I've had success doing this on Firefox, I haven't really tested it out on other browsers though. You can look at HTMLParser.js in the AtropaToolbox for an example of using document.implementation methods. I've used this bit of script to XMLHttpRequest pages and manipulate them or extract data from them. Scripts in the page are not executed though, which is what I wanted though it may not be what you want. The reason I went with this rather verbose method instead of trying to use the parsing available from the XMLHttpRequest object directly was that I ran into quite a bit of trouble with parsing errors at the time and I wanted to specify that the doc should be parsed as HTML 4 Transitional because it seems to take all kinds of slop and produce a DOM.
There is also a DOMParser available which may be easier for you to use. There is an implementation by Eli Grey on the page at MDN for browsers that don't have the DOMParser but do support document.implementation.createHTMLDocument. The specs for DOMParser specify that scripts in the page are not executed and the contents of noscript tags be rendered.
If you really need scripts enabled in the page you could create an iFrame with 0 height, 0 width, no borders, etc. It would still be in the page but you could hide it pretty well.
There's also the option of using window.open() with document.write, DOM methods or whatever you like. Some browsers even let you do data URI's now.
var x = window.open( 'data:text/html;base64,' + btoa('<h1>hi</h1>') );
// wait for the document to load. It only takes a few milliseconds
// but we'll wait for 5 seconds so you can watch the child window
// change.
setTimeout(function () {
console.log(x.document.documentElement.outerHTML);
x.console.log('this is the console in the child window');
x.document.body.innerHTML = 'oh wow';
}, 5000);
So, you do have a few options for creating whole documents offscreen/hidden and manipulating them, all of which support loading the document from strings.
There's also phantomjs, an awesome project producing a headless scriptable web browser based on webkit. You'll have access to the local filesystem and be able to do pretty much whatever you want. I don't really know what you're trying to accomplish with your full page scripting and manipulation.
For a Firefox add-on, it probably makes more sense to use the document.implementation.createHTMLDocument method, and then go from the DOM that gives you.
With a document fragment you would append elements that you had created with document.createElement('yourElement'). aWholeHTMLDocument is merely text. Also, unless your using frames I'm not sure why you would need to create the whole HTML document just use what is inside the <body> tags.
Use appendChild
see https://developer.mozilla.org/en-US/docs/Web/API/Document/createDocumentFragment
var fragment = document.createDocumentFragment();
... fragment.appendChild(some element);
document.querySelector('blah').appendChild(fragment);
Here is a solution for converting a HTML string into a DOM object:
let markup = '<!doctype html><html><head></head><body><h1>hello world</h1></body></html>';
let range = document.createRange();
let fragment = range.createContextualFragment(markup); //Creates a DOM object
The string does not need to be a complete HTML document.
Use querySelector() to get a child of the document fragment (you probably want the body, or some child of the body). Then get the innerHTML.
document.body.innerHTML = aWholeHTMLDocument.querySelector("body").innerHTML
or
aWholeHTMLDocument.querySelector("body").childNodes;
See https://developer.mozilla.org/en-US/docs/Web/API/DocumentFragment.querySelector

Is it possible to get jquery objects from an html string thats not in the DOM?

For example in javascript code running on the page we have something like:
var data = '<html>\n <body>\n I want this text ...\n </body>\n</html>';
I'd like to use and at least know if its possible to get the text in the body of that html string without throwing the whole html string into the DOM and selecting from there.
First, it's a string:
var arbitrary = '<html><body>\nSomething<p>This</p>...</body></html>';
Now jQuery turns it into an unattached DOM fragment, applying its internal .clean() method to strip away things like the extra <html>, <body>, etc.
var $frag = $( arbitrary );
You can manipulate this with jQuery functions, even if it's still a fragment:
alert( $frag.filter('p').get() ); // says "<p>This</p>"
Or of course just get the text content as in your question:
alert( $frag.text() ); // includes "This" in my contrived example
// along with line breaks and other text, etc
You can also later attach the fragment to the DOM:
$('div#something_real').append( $frag );
Where possible, it's often a good strategy to do complicated manipulation on fragments while they're unattached, and then slip them into the "real" page when you're done.
The correct answer to this question, in this exact phrasing, is NO.
If you write something like var a = $("<div>test</div>"), jQuery will add that div to the DOM, and then construct a jQuery object around it.
If you want to do without bothering the DOM, you will have to parse it yourself. Regular expressions are your friend.
It would be easiest, I think, to put that into the DOM and get it from there, then remove it from the DOM again.
Jquery itself is full of tricks like this. It's adding all sorts off stuff into the DOM all the time, including when you build something using $('<p>some html</p>'). So if you went down that road you'd still effectively be placing stuff into the DOM then removing it again, temporarily, except that it'd be Jquery doing it.
John Resig (jQuery author) created a pure JS HTML parser that you might find useful. An example from that page:
var dom = HTMLtoDOM("<p>Data: <input disabled>");
dom.getElementsByTagName("body").length == 1
dom.getElementsByTagName("p").length == 1
Buuuut... This question contains a constraint that I think you need to be more critical of. Rather than working around a hard-coded HTML string in a JS variable, can you not reconsider why it's that way in the first place? WHAT is that hard-coded string used for?
If it's just sitting there in the script, re-write it as a proper object.
If it's the response from an AJAX call, there is a perfectly good jQuery AJAX API already there. (Added: although jQuery just returns it as a string without any ability to parse it, so I guess you're back to square one there.)
Before throwing it in the DOM that is just a plain string.
You can sure use REGEX.

How do I get my widget not to crash if there is no value in a xml node?

I'm getting an xml file and want to get data from it.
The source of the xml doesn't really matter but what I;ve got to get a certain field is:
tracks = xmlDoc.getElementsByTagName("track");
variable = tracks.item(i).childNodes.item(4).childNodes.item(0).nodeValue;
Now this works like a charm, EXCEPT when there is no value in the node. So if the structure is like this:
<xml>
<one>
<two>nodeValue</two>
</one>
<one>
<two></two>
</one>
</xml>
the widget will crash on the second 'one' node, because there is no value in the 'two' node. The console says:
TypeError: tracks.item(i).childNodes.item(4).childNodes.item(0) has no properties
Any ideas on how to get the widget to just see empty as an empty string (null, empty, or ""), instead of crashing? I'm guessing something along the lines of data, getValue(), text, or something else.
using
var track= xmlDoc.getElementsByTagName('track')[0];
var info= track.getElementsByTagName('artist')[0];
var value= info.firstChild? info.firstChild.data : '';
doesn't work and returns "TypeError: track has no properties". That's from the second line where artist is called.
Test that the ‘two’ node has a child node before accessing its data.
childNodes.item(i) (or the JavaScript simple form childNodes[i]) should generally be avoided, it's a bit fragile relying on whitespace text nodes being in the exact expected place.
I'd do something like:
var tracks= xmlDoc.getElementsByTagName('track')[0];
var track= tracks.getElementsByTagName('one')[0];
var info= track.getElementsByTagName('two')[0];
var value= info.firstChild? info.firstChild.data : '';
(If you don't know the tagnames of ‘one’ and ‘two’ in advance, you could always use ‘getElementsByTagName('*')’ to get all elements, as long as you don't need to support IE5, where this doesn't work.)
An alternative to the last line is to use a method to read all the text inside the node, including any of its child nodes. This doesn't matter if the node only ever contains at most one Text node, but can be useful if the tree can get denormalised or contain EntityReferences or nested elements. Historically one had to write a recurse method to get this information, but these days most browsers support the DOM Level 3 textContent property and/or IE's innerText extension:
var value= info.textContent!==undefined? info.textContent : info.innerText;
without a dtd that allows a one element to contain an empty two element, you will have to parse and fiddle the text of your xml to get a document out of it.
Empty elements are like null values in databases- put in something, a "Nothing" or "0" value, a non breaking space, anything at all- or don't include the two element.
Maybe it could be an attribute of one, instead of an element in its own right.
Attributes can have empty strings for values. Better than phantom elements .
Yahoo! Widgets does not implement all basic javascript functions needed to be able to use browser-code in a widget.
instead of using:
tracks = xmlDoc.getElementsByTagName("track");
variable = tracks.item(i).childNodes.item(4).childNodes.item(0).nodeValue;
to get values it's better to use Xpath with a direct conversion to string. When a string is empty in Yahoo! Widgets it doesn't give any faults, but returns the 'empty'. innerText and textContent (the basic javascript way in browsers, used alongside things like getElementsByTagName) are not fully (or not at all) implemented in the Yahoo! Widgets Engine and make it run slower and quite awfully react to xmlNodes and childNodes. an easy way however to traverse an xml Document structure is using 'evaluate' to get everything you need (including lists of nodes) from the xml.
After finding this out, my solution was to make everything a lot easier and less sensitive to faults and errors. Also I chose to put the objects in an array to make working with them easier.
var entries = xmlDoc.evaluate("lfm/recenttracks/track");
var length = entries.length;
for(var i = 0; i < length; i++) {
var entry = entries.item(i);
var obj = {
artist: entry.evaluate("string(artist)"),
name: entry.evaluate("string(name)"),
url: entry.evaluate("string(url)"),
image: entry.evaluate("string(image[#size='medium'])")
};
posts[i] = obj;
}

jquery: fastest DOM insertion?

I got this bad feeling about how I insert larger amounts of HTML.
Lets assume we got:
var html="<table>..<a-lot-of-other-tags />..</table>"
and I want to put this into
$("#mydiv")
previously I did something like
var html_obj = $(html);
$("#mydiv").append(html_obj);
Is it correct that jQuery is parsing html to create DOM-Objects ? Well this is what I read somewhere (UPDATE: I meant that I have read, jQuery parses the html to create the whole DOM tree by hand - its nonsense right?!), so I changed my code:
$("#mydiv").attr("innerHTML", $("#mydiv").attr("innerHTML") + html);
Feels faster, is it ? And is it correct that this is equivalent to:
document.getElementById("mydiv").innerHTML += html ? or is jquery doing some additional expensive stuff in the background ?
Would love to learn alternatives as well.
Try the following:
$("#mydiv").append(html);
The other answers, including the accepted answer, are slower by 2-10x: jsperf.
The accepted answer does not work in IE 6, 7, and 8 because you can't set innerHTML of a <table> element, due to a bug in IE: jsbin.
innerHTML is remarkably fast, and in many cases you will get the best results just setting that (I would just use append).
However, if there is much already in "mydiv" then you are forcing the browser to parse and render all of that content again (everything that was there before, plus all of your new content). You can avoid this by appending a document fragment onto "mydiv" instead:
var frag = document.createDocumentFragment();
frag.innerHTML = html;
$("#mydiv").append(frag);
In this way, only your new content gets parsed (unavoidable) and the existing content does not.
EDIT: My bad... I've discovered that innerHTML isn't well supported on document fragments. You can use the same technique with any node type. For your example, you could create the root table node and insert the innerHTML into that:
var frag = document.createElement('table');
frag.innerHTML = tableInnerHtml;
$("#mydiv").append(frag);
What are you attempting to avoid? "A bad feeling" is incredibly vague. If you have heard "the DOM is slow" and decided to "avoid the DOM", then this is impossible. Every method of inserting code into a page, including innerHTML, will result in DOM objects being created. The DOM is the representation of the document in your browser's memory. You want DOM objects to be created.
The reason why people say "the DOM is slow" is because creating elements with document.createElement(), which is the official DOM interface for creating elements, is slower than using the non-standard innerHTML property in some browsers. This doesn't mean that creating DOM objects is bad, it is necessary to create DOM objects, otherwise your code wouldn't do anything at all.
The answer about using a DOM fragment is on the right track. If you have a bunch of html objects that you are constant inserting into the DOM then you will see some speed improvements using the fragment. This post by John Resig explains it pretty well:
http://ejohn.org/blog/dom-documentfragments/
The fastest way to append items
The fastest way to append to the DOM tree is to buffer all of your append in to a single DOM fragment, then append the dom fragment to the dom.
This is the method I use in my game engine.
//Returns a new Buffer object
function Buffer() {
//the framgment
var domFragment = document.createDocumentFragment();
//Adds a node to the dom fragment
function add(node) {
domFragment.appendChild(node);
}
//Flushes the buffer to a node
function flush(targetNode) {
//if the target node is not given then use the body
var targetNode = targetNode || document.body;
//append the domFragment to the target
targetNode.appendChild(domFragment);
}
//return the buffer
return {
"add": add,
"flush": flush
}
}
//to make a buffer do this
var buffer = Buffer();
//to add elements to the buffer do the following
buffer.add(someNode1);
//continue to add elements to the buffer
buffer.add(someNode2);
buffer.add(someNode3);
buffer.add(someNode4);
buffer.add(someN...);
//when you are done adding nodes flush the nodes to the containing div in the dom
buffer.flush(myContainerNode);
Using this object i am able to render ~1000 items to the screen ~40 times a second in firefox 4.
Here's a use case.
For starters, write a script that times how long it takes to do it 100 or 1,000 times with each method.
To make sure the repeats aren't somehow optimized away--I'm no expert on JavaScript engines--vary the html you're inserting every time, say by putting '0001' then '0002' then '0003' in a certain cell of the table.
I create a giant string with and then append this string with jquery.
Works good and fast, for me.
You mention being interested in alternatives. If you look at the listing of DOM-related jQuery plugins you'll find several that are dedicated to programatically generating DOM trees. See for instance SuperFlyDom or DOM Elements Creator; but there are others.

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