CODEWITHSUNDEEP
javascriptxmldom
Bonte
Bonte

Reputation: 9

testing to see if you have empty text node in xml

Using Ajax to fetch XML data. question about blank text nodes

I read this question/ answer here Javascript/XML - Getting the node name

and this helped my understanding a ton about how the structure is set up however I still have a question or two.. when he mentions this part:

"Text node with a carriage return and some spaces or tab"

How would you test to see f you have gotten an empty text node like this? I've tried testing to see:

if nodeValue == null
nodeValue == "null"
nodeValue == ""
nodeValue == " "

none of these appear to be working

I figured maybe the length would be 0 so I tested for .length and it returned 5 (1 return key and 4 tabs.. added an extra tab in there and tested again it returned 6)

I then googled how to remove whitespace and used these:

.replace(/\s+/g, ' ');
.replace(/^\s+|\s+$/g, '');

Neither worked and still said the .length was still 5

Reason I want to test for this is because what if I don't know each of the element node names before hand or exactly how the DOM is set up.

Or is there a better way to navigate without bothering to check if a text node is just the tabs/spaces/return key?

Upvotes: 0

Views: 3927

Answers (1)

T.J. Crowder
T.J. Crowder

Reputation: 1074989

.replace(/^\s+|\s+$/g, ''); works unless the spaces/tabs aren't really spaces and tabs, but one of the various other Unicode space-like characters. So I'm guessing you weren't quite using it correctly.

This would be how to use it:

if (!textNode.nodeValue.replace(/^\s+|\s+$/g, '')) {
    // Node is empty
}

Example: Live Copy | Live Source

var xml = parseXml("<test>\n\t\t\t</test>");
var textNode = xml.documentElement.firstChild;
display("textNode.nodeValue.length = " +
        textNode.nodeValue.length);
display('Is "empty"? ' +
        (!textNode.nodeValue.replace(/^\s+|\s+$/g, '')));

function display(msg) {
  var p = document.createElement('p');
  p.innerHTML = String(msg);
  document.body.appendChild(p);
}

Output:

textNode.nodeValue.length = 4
Is "empty"? true

(Where parseXML is from this answer.)

But we really don't need to do a replace (although the overhead of doing it is trivial). A test like this would do it:

if (/^\s*$/.test(textNode.nodeValue)) {
    // The node is "empty"
}

That regular expression (zero or more whitespace characters with anchors at both ends) will only match a string that's already empty or consists only of whitespace characters.

Upvotes: 2

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