how to handle NULL from a data request using QML doc.responseXML.documentElement

[biskero]

Hello,

I am trying to handle NULL from a data request using QML doc.responseXML.documentElement:

if (doc.readyState === XMLHttpRequest.DONE) {
                //Check is not NULL
                if(!doc.responseXML.documentElement) {
                    var a = doc.responseXML.documentElement;


                }
}

but I get that an error: TypeError: Value is null and could not be converted to an object
So how do I catch null value coming from the doc.responseXML.documentElement ?

thx

[raven-worx]

@biskero
please show the whole code handling your XMLHttpRequest

[biskero]

This post is deleted!

[biskero]

This is the code, data is received correctly but after the check DONE, I want to make sure if not NULL but I get the error:
TypeError: Value is null and could not be converted to an object

on the var a = doc.responseXML.documentElement; code line

if (doc.readyState === XMLHttpRequest.DONE) {
                //Check is not NULL
                if(!doc.responseXML.documentElement) {
                    var a = doc.responseXML.documentElement;
for (var ii = 0; ii < a.childNodes.length; ++ii) {
                        //showRequestInfo(a.childNodes[ii].nodeName);
                        if(a.childNodes[ii].nodeName === "light") {
                            console.log("a="+a.childNodes[ii].childNodes[0].nodeValue);
                        }
}
}

[raven-worx]

@biskero
also the code before that block

[biskero]

if (doc.readyState === XMLHttpRequest.LOADING) {
                //Do something while loading

            } else if (doc.readyState === XMLHttpRequest.HEADERS_RECEIVED) {
                //showRequestInfo("Headers -->");
                //showRequestInfo(doc.getAllResponseHeaders ());
                //showRequestInfo("Last modified -->");
                //showRequestInfo(doc.getResponseHeader ("Last-Modified"));

            } else if (doc.readyState === XMLHttpRequest.DONE) {
                //Check is not NULL
                if(!doc.responseXML.documentElement) {
                    var a = doc.responseXML.documentElement;
for (var ii = 0; ii < a.childNodes.length; ++ii) {
                        //showRequestInfo(a.childNodes[ii].nodeName);
                        if(a.childNodes[ii].nodeName === "light") {
                            console.log("a="+a.childNodes[ii].childNodes[0].nodeValue);
                        }
}
}

[raven-worx]

@biskero
ok once more.
I am not interested in any more detail implementations from the inside of your function, showing code beyond the point you want to do your check isnt relevant.
I want to see the code beginning from where you create the XMLHttpRequest object.

[biskero]

the code come from this example

 MouseArea {
            id: mouseArea
            anchors.fill: parent
            onClicked: {
                log.text = ""
                console.log("\n")

                var doc = new XMLHttpRequest();
                doc.onreadystatechange = function() {
                    if (doc.readyState == XMLHttpRequest.HEADERS_RECEIVED) {
                        showRequestInfo("Headers -->");
                        showRequestInfo(doc.getAllResponseHeaders ());
                        showRequestInfo("Last modified -->");
                        showRequestInfo(doc.getResponseHeader ("Last-Modified"));

                    } else if (doc.readyState == XMLHttpRequest.DONE) {
                        var a = doc.responseXML.documentElement;
                        for (var ii = 0; ii < a.childNodes.length; ++ii) {
                            showRequestInfo(a.childNodes[ii].nodeName);
                        }
                        showRequestInfo("Headers -->");
                        showRequestInfo(doc.getAllResponseHeaders ());
                        showRequestInfo("Last modified -->");
                        showRequestInfo(doc.getResponseHeader ("Last-Modified"));
                    }
                }

                doc.open("GET", "data.xml");
                doc.send();
            }
        }

I just add the code to check the if object is not NULL

if(!doc.responseXML.documentElement)

[raven-worx]

@biskero

1. try console.log(doc.responseXML.documentElement) and console.log(typeof doc.responseXML.documentElement) and check the console output, it might give some help
2. where does this file come from? its important what the Content-Type is of the response.
3. try doc.responseXML.documentElement == null or doc.responseXML.documentElement == undefined