binding DOM elements in DoRun is not persistent?
lazarus / 76-Pas2JS

----------------------------------------------------------------------
nomorelogic · 2022-05-22 17:04

hi all
I'm playing with pas2js reproducing an example found in blaise pascal
magazine.

Development environment is Lazarus 2.2.2 + Pas2Js 2.2.0.
Follow some code from attached project:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TMyApplication.doRun; begin  // Your code here  BindElements; 
btnLogin.AddEventListener('click',@DoLoginCLick);  
Terminate;end; procedure TMyApplication.BindElements;begin 
Writeln('BindElements'); 
edtEmail:=TJSHTMLInputElement(GetHTMLElement('edtEmail')); 
edtPassword:=TJSHTMLInputElement(GetHTMLElement('edtPassword'));  btnL
ogin:=TJSHTMLButtonElement(GetHTMLElement('btnLogin'));end; procedure
TMyApplication.doLoginClick(aEvent: TJSEvent);begin 
Writeln('doLoginClick');  // BindElements;   // <- uncomment and all
works!  writeln('edtEmail.Value = ', edtEmail.value);    // <- this
give the error  DoServerLogin(edtEmail.Value,edtPassword.Value);end; 
At runtime, if I click on LoginButton I get this error:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
project_login.lpr:45 Uncaught TypeError: Cannot read properties of
undefined (reading 'value')    at Object.doLoginClick
(project_login.lpr:45:40)    at HTMLButtonElement.cb (rtl.js:249:1) 
Anyway if I uncomment "// BindElements" from "procedure
TMyApplication.doLoginClick(aEvent: TJSEvent)"  all works well...

Where I'm wrong?

thanks
nomorelogic

----------------------------------------------------------------------
nomorelogic · 2022-05-24 07:47

I got the solution from Michael Van Canneyt
follows the solution

QuoteNormally the bind should be persistent. I use the described
technique since several years meanwhile.
Please check if your program code contains an Application.Free after
the Application.Run.
If it does, remove it.
Earlier versions of Lazarus generated this statement erroneously when
using
the 'new web application' wizard.