I have an XML that I'm trying to get a sum out of. The number is either 0 or 1, and I want to get a sum of all the numbers. The XML looks like this:

<alerts>
    <alert1>0</alert1>
    <alert2>1</alert2>
    <alert3>1</alert3>
    <alert4>0</alert4>
</alerts>

My current code (wrong) looks like this:

xpath = require('xpath');
xmldom = require('xmldom');

doc = new xmldom.DOMParser().parseFromString("sourceXml");

var count = xpath.select("alerts/alert1", doc).toString();
count  = xpath.select("alerts/alert2", doc).toString();
count  = xpath.select("alerts/alert3", doc).toString();
count  = xpath.select("alerts/alert4", doc).toString();


var result = count;

Obviously since they're strings it results in "0110" as a string and not "2" as an INT. I tried wrapping each in parseInt but that just returns NaN. Any help would be appreciated.

Edit:

parseInt(xpath.select("alerts/alert3", doc).toString());

parseInt(xpath.select("alerts/alert3", doc)); 

Tried both but I'm not very experienced with JavaScript so it could be a syntax issue.

CodePudding user response：

From the xpath.select() documentation...

The return value is determined based on the result type of the expression (which can always be predicted ahead of time based on the expression's syntax):

• A boolean value if the expression evaluates to a boolean value.
• A number if the expression evaluates to a numeric value.
• A string if the expression evaluates to a string.
• If the expression evaluates to a nodeset:
  • An array of 0 or more nodes if single is unspecified or falsy
  • A single node (the first node in document order) or undefined if single is truthy

All your results are arrays, each containing a single node.

You can actually coerce the values to be numeric automatically by using the XPath number function

const count = xpath.select("number(alerts/alert1)", doc)
   xpath.select("number(alerts/alert2)", doc)
   xpath.select("number(alerts/alert3)", doc)
   xpath.select("number(alerts/alert4)", doc)

Perhaps an easier option would be to simply use the XPath sum function

const count = xpath.select(
  "sum(alerts/*[self::alert1 or self::alert2 or self::alert3 or self::alert4])",
  doc
)

_{See also XPath to select multiple tags}