get elements by attribute value

Question

I am sending a request via webservices in Javascript and the response i am receiving is like this:

<ListOfBook>
<Book>
    <Id>ACIA-11QWTKX</Id>
    <ListOfBookUser recordcount="0" lastpage="true">
    </ListOfBookUser>
</Book>
<Book>
    <Id>ACIA-ANC0CC</Id>
    <ListOfBookUser recordcount="1" lastpage="true">
        <BookUser>
            <BookId>ACIA-ANC0CC</BookId>
            <BookName>TKSP_GLOBAL</BookName>
        </BookUser>
        </ListOfBookUser>
</Book>                             
<Book>
    <Id>ACIA-ANC0CF</Id>
    <ListOfBookUser recordcount="0" lastpage="true">
    </ListOfBookUser>
</Book>
<Book>
    <Id>ACIA-EUMCH5</Id>
    <ListOfBookUser recordcount="1" lastpage="true">
        <BookUser>
            <BookId>ACIA-EUMCH5</BookId>
            <BookName>TKSP_MADRID_CENTRO_SUR</BookName>
        </BookUser>
    </ListOfBookUser>
</Book>

As you can see there are some elements of <Book> that have a child <BookUser> and there are other elements that doesn't have this child.

I need a way to extract elements of <Book> that have the <BookUser> child with regular expressions , DOM or Xpath . Any suggestions please ?

Answer 1

Using xpath you can do this to extract all Book elements that have BookUser descendants (you need to look for descendants not for children, since your BookUsers are contained inside ListOfBookUser tags:

//Book[descendant::BookUser]

or

//Book[.//BookUser]

or (as @MartinHonnen showed in the comments):

//Book[ListOfBookUser/BookUser]

Answer 2

Try to see:

[MDN] https://developer.mozilla.org/en-US/docs/Introduction_to_using_XPath_in_JavaScript

[W3Schools] : http://www.w3schools.com/xsl/xpath_examples.asp

.evaluate function is usefull.

Answer 3

You can use XPath with an expression like //Book[ListOfBookUser/BookUser] :

 var xmlMarkup = `<ListOfBook> <Book> <Id>ACIA-11QWTKX</Id> <ListOfBookUser recordcount="0" lastpage="true"> </ListOfBookUser> </Book> <Book> <Id>ACIA-ANC0CC</Id> <ListOfBookUser recordcount="1" lastpage="true"> <BookUser> <BookId>ACIA-ANC0CC</BookId> <BookName>TKSP_GLOBAL</BookName> </BookUser> </ListOfBookUser> </Book> <Book> <Id>ACIA-ANC0CF</Id> <ListOfBookUser recordcount="0" lastpage="true"> </ListOfBookUser> </Book> <Book> <Id>ACIA-EUMCH5</Id> <ListOfBookUser recordcount="1" lastpage="true"> <BookUser> <BookId>ACIA-EUMCH5</BookId> <BookName>TKSP_MADRID_CENTRO_SUR</BookName> </BookUser> </ListOfBookUser> </Book> </ListOfBook>`; var xmlDoc = new DOMParser().parseFromString(xmlMarkup, 'application/xml'); var bookSnapshot = xmlDoc.evaluate('//Book[ListOfBookUser/BookUser]', xmlDoc, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null); for (var i = 0, l = bookSnapshot.snapshotLength; i < l; i++) { var book = bookSnapshot.snapshotItem(i); var id = xmlDoc.evaluate('Id', book, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null).singleNodeValue; if (id != null) { console.log(id.textContent); } }

For brevity of the sample, I have used the multi-line string literal delimiters `` only implemented in actual browsers, but the XPath API is supported in DOM implementations in Mozilla, Chrome, Safari and Edge.