[Pas2js] TJSXMLHttpRequest questions

[Mattias Gaertner]

On Sun, 20 May 2018 15:59:37 +0700
Ryan Joseph <ryan at thealchemistguild.com> wrote:

> 1) How are we intended to use TJSOnReadyStateChangeHandler? I thought the callback would take a parameter to the TJSXMLHttpRequest but it doesn’t. The JavaScript way seems to be a closure so we can access the request in the same scope but we obviously don’t have those in Pascal.

There are no anonymous methods yet, but there are closures:

procedure Test;
var
  xhr : TJSXMLHttpRequest;

  procedure HandleLoaded;
  begin
    if (xhr.readyState = 4) or (xhr.status = 200) then
      writeln(xhr.responseText);
  end;

begin
  xhr := TJSXMLHttpRequest.new;
  xhr.open('GET', 'file.html');
  xhr.onreadystatechange := @HandleLoaded;
  xhr.send;
end;


> 2) Not really Pascal related but why does HandleLoadedFile get called 3 times? I had to call abort manually to stop it once I got the text I wanted.

See
https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/onreadystatechange

Btw, normally you use OnLoad:
  xhr.addEventListener('load', @OnLoad);

Mattias