Update REST API SharePoint Online

Question

I execute this function updatemainop() in my script:

function updatemainop() {
    var itemType = GetItemTypeForListName('MainOperation');
    var query = applink + "_api/SP.AppContextSite(@target)/web/lists/getbytitle('MainOperation')/items(125)?&@target='" + hostweblink + "'";

    var meta_data = {"__metadata": { "type": itemType }, "AMOUNTBUDGET": 1500};
    var executor = new SP.RequestExecutor(applink);

    executor.executeAsync({
        url : query,
        method : "POST",
        body: JSON.stringify(meta_data),
        headers: {
            "Accept": "application/json;odata=verbose",
            "Content-Type" : "application/json;odata=verbose",
            "X-HTTP-Method": "MERGE",
            "IF-MATCH": "*"
        },
        success: function (data) {
            console.log(JSON.stringify(data));
        },
        error: function (err) {
            console.log(JSON.stringify(err));
        }


       });
      }

but I have this error :

"NetworkError: 404 NOT FOUND - https://mycompany-b10b99295a3aa7.sharepoint.com/sites/mysite/myproject/SP.AppContextSite(@target)/web/lists/getbytitle('MainOperation')/items(125)?&@target=%27https://mycompany.sharepoint.com/sites/myproject%27" items(1...CLAUSE' {"responseAvailable":true,"body":"404 NOT FOUND","statusCode":404,"statusText":"NOT FOUND","contentType":null,"allResponseHeaders":"Cache-Control: private,max-age=0\r\nContent-Length: 13\r\nExpires: Tue, 23 Aug 2016 08:27:54 GMT\r\nAccept-Ranges: bytes\r\nServer: Microsoft-IIS/8.5\r\nX-SharePointHealthScore: 0\r\nPublic-Extension: http://schemas.microsoft.com/repl-2\r\nSPRequestGuid: f85ea19d-70bc-3000-b229-65ed29d0e1fe\r\nrequest-id: f85ea19d-70bc-3000-b229-65ed29d0e1fe\r\nStrict-Transport-Security: max-age=31536000\r\nX-Frame-Options: SAMEORIGIN\r\nSPRequestDuration: 123\r\nSPIisLatency: 4\r\nX-Powered-By: ASP.NET\r\nMicrosoftSharePointTeamServices: 16.0.0.5701\r\nX-Content-Type-Options: nosniff\r\nX-MS-InvokeApp: 1; RequireReadOnly\r\nP3P: CP=\"ALL IND DSP COR ADM CONo CUR CUSo IVAo IVDo PSA PSD TAI TELo OUR SAMo CNT COM INT NAV ONL PHY PRE PUR UNI\"\r\nDate: Wed, 07 Sep 2016 08:27:53 GMT\r\n","headers":{"CACHE-CONTROL":"private,max-age=0","CONTENT-LENGTH":"13","EXPIRES":"Tue, 23 Aug 2016 08:27:54 GMT","ACCEPT-RANGES":"bytes","SERVER":"Microsoft-IIS/8.5","X-SHAREPOINTHEALTHSCORE":"0","PUBLIC-EXTENSION":"http://schemas.microsoft.com/repl-2","SPREQUESTGUID":"f85ea19d-70bc-3000-b229-65ed29d0e1fe","REQUEST-ID":"f85ea19d-70bc-3000-b229-65ed29d0e1fe","STRICT-TRANSPORT-SECURITY":"max-age=31536000","X-FRAME-OPTIONS":"SAMEORIGIN","SPREQUESTDURATION":"123","SPIISLATENCY":"4","X-POWERED-BY":"ASP.NET","MICROSOFTSHAREPOINTTEAMSERVICES":"16.0.0.5701","X-CONTENT-TYPE-OPTIONS":"nosniff","X-MS-INVOKEAPP":"1; RequireReadOnly","P3P":"CP=\"ALL IND DSP COR ADM CONo CUR CUSo IVAo IVDo PSA PSD TAI TELo OUR SAMo CNT COM INT NAV ONL PHY PRE PUR UNI\"","DATE":"Wed, 07 Sep 2016 08:27:53 GMT"}}

Answer 1

If you are receiving a 404 NOT Found http error code most likely your URL formation was not correct. From the error message it appears that you are trying to reach a site /sites/myproject in your hostweblink variable. Are you sure you have such a site or did you intend to reach /sites/mysite/myproject?