REST GET using SharePoint hosted app

Question

I've been testing an outgoing REST GET request (towards the other world, not towards SharePoint).

When I'm using this code in pure JavaScript/HTML it works just fine. But when using it in my SharePoint app I'm receiving a JavaScript runtime error:

NetworkError at client.send(null);

This is the code I've tried so far:

var url = "https://test.com/example/something/1";

var client = new XMLHttpRequest();

client.open("GET", url, false);

client.setRequestHeader("Content-Type", "application/json");
client.setRequestHeader("theplatform", "default");
client.setRequestHeader("Authorization", "Basic keyofsomethingvalue%");

client.send(null);     

if (client.status == 200)
    alert("The request succeeded!\n\nThe response representation was:\n\n" + client.responseText)
else
    alert("The request did not succeed!\n\nThe response status was: " + client.status + " " + client.statusText + ".");

Does anybody know what I did wrong?

Answer 1

CSOM and the REST API include the WebProxy for these operations.

Query a remote service using the web proxy in SharePoint 2013

Code sample:

$.ajax({
    url: "../_api/SP.WebProxy.invoke",
    type: "POST",
    data: JSON.stringify(
        {
            "requestInfo": {
                "__metadata": { "type": "SP.WebRequestInfo" },
                "Url": url,
                "Method": "GET",
                "Headers": {
                    "results": [{
                        "__metadata": { "type": "SP.KeyValue" },
                        "Key": "Accept",
                        "Value": "application/json;odata=verbose",
                        "ValueType": "Edm.String"
                    }]
                }
            }
        }),
    headers: {
        "Accept": "application/json;odata=verbose",
        "Content-Type": "application/json;odata=verbose",
        "X-RequestDigest": $("#__REQUESTDIGEST").val()
    },
    success: successHandler,
    error: errorHandler
});

Note 1: You need to register the target domain as a remote endpoint in the app manifest.

Note 2: Response size must not exceed 200 Kb.