Dealing with 404 url error in module.

[justjim1220]

this is an example of the XMLHttpRequest mentioned in the previous post…

var xmlHttp = null;

function GetCustomerInfo()
{
    var CustomerNumber = document.getElementById( "TextBoxCustomerNumber" ).value;
    var Url = "GetCustomerInfoAsJson.aspx?number=" + CustomerNumber;

    xmlHttp = new XMLHttpRequest(); 
    xmlHttp.onreadystatechange = ProcessRequest;
    xmlHttp.open( "GET", Url, true );
    xmlHttp.send( null );
}

function ProcessRequest() 
{
    if ( xmlHttp.readyState == 4 && xmlHttp.status == 200 ) 
    {
        if ( xmlHttp.responseText == "Not found" ) 
        {
            document.getElementById( "TextBoxCustomerName"    ).value = "Not found";
            document.getElementById( "TextBoxCustomerAddress" ).value = "";
        }
        else
        {
            var info = eval ( "(" + xmlHttp.responseText + ")" );

            // No parsing necessary with JSON!        
            document.getElementById( "TextBoxCustomerName"    ).value = info.jsonData[ 0 ].cmname;
            document.getElementById( "TextBoxCustomerAddress" ).value = info.jsonData[ 0 ].cmaddr1;
        }                    
    }
}

[justjim1220]

and this example uses jQuery…

< script>
$(document).ready(function(){
    $("button").click(function(){
        $.get("demo_test.asp", function(data, status){
            alert("Data: " + data + "\nStatus: " + status);
        });
    });
});
< /script>

you would have to download or call jquery…

downloaded and added to your module directory…

getScripts: function() {
    return ["jquery.min.js'];
},

to call for it…

< script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js">< /script>

[Mykle1]

@justjim1220

I appreciate you trying to help but I could have kept googling myself. I’m looking for an explanation, too, and not just a random “try this!”. Thanks

[sdetweil]

@mykle1 sorry, you are using some words that don’t describe well what the problem is…

i THINK you said

when I try to load image files (local to the MM system), I use a URL string. 
that URL string is 'relative' to the base of my server, defined by '??????' (you didn't supply that)

when a URL fails to load, I get error 404. (not found). 

but how do I handle this?

you would add an onerror() handler for the img object
this will get called ONLY when there is an error

img.onerror = funtion(event_object){
var img_with_error = event_object.currentTarget
img_with_error.src=??? the url of the failing image
}

see https://www.w3schools.com/jsref/obj_event.asp
for more info in decoding the event object

[Mykle1]

@sdetweil said in Dealing with 404 url error in module.:

sorry, you are using some words that don’t describe well what the problem is…

Yes, I’m sorry about the description but you understood my meaning, so thank you for that. :thumbsup:

Your onerror() handler suggestion is/was exactly what I needed/wanted and works beautifully. Again, thank you. I do appreciate that you took the time to give me advice/assistance. Here is the finished, working tag:

  // picture
            var img = document.createElement("img");
            img.classList.add("photo");
            img.src = EOL.eolMediaURL;
            img.onerror = function(event_object) { //  This function replaces broken image
            var img_with_error = event_object.currentTarget //  This function replaces broken image
            img_with_error.src= "modules/MMM-EOL/images/darwin.jpg" // This is the path to the replacement image
           }
            wrapper.appendChild(img);

I would be remiss if I did not thank @cowboysdude, as well, for his help on this module.

[sdetweil]

@mykle1 note that your onerror handler could get stuck in a loop IF the forced replacement url also fails

[Mykle1]

@sdetweil

That’s good to know. Thanks to you again. If you were in NYC I would buy you a beer (or many). :-)

[cowboysdude]

@mykle1 @sdetweil came up with a beautiful answer…I didn’t do a thing LOL