Using XMLHttpRequest() in Transcrypt

Question

I only have minimal JavaScript knowledge from coding a small API site entirely client-side.

How would I use XMLHttpRequest() in Transcrypt? Or should I be using URLlib or something else?

Is it as simple as creating a new XMLHttpRequest object and then sending the data or retrieving a page as in JS?

XHR = XMLHttpRequest()
XHR.open("POST", "https://example.com/cors.php")

Answer 1

It's indeed just as simple as in JS, only with Python syntax:

def read_file():
    xmlhttp= __new__ (XMLHttpRequest())
    xmlhttp.open('GET', 'https://github.com/QQuick/Transcrypt/blob/master/README.rst', False);
    xmlhttp.send()
    console.log(xmlhttp.responseText)

In your example that would be:

XHR = __new__ (XMLHttpRequest())
XHR.open("POST", "https://example.com/cors.php")

Note the __new__ () function. In JavaScript it would have been the new operator but Python syntax doesn't allow that.

If you want to avoid __new__ () altogether you may encapsulate XMLHttpRequest i a true Python class (it's a JS function now), but there's no need to.

See

http://www.transcrypt.org/docs/html/special_facilities.html#creating-javascript-objects-with-new-constructor-call

for a general explantion on using or avoiding __new__ ().

You may also go via JQuery as in the following somewhat bigger example:

__pragma__ ('alias', 'jq', '$')
__pragma__ ('noalias', 'clear')

# For use by eval'ed turtle applet
import turtle
import random
import math

def clear ():
    editor.setValue ('')
    turtle.reset ()
    run ()

def run ():
    def success (result):
        global random

        turtle.reset ()
        rnd = random
        eval (result)
        random = rnd

    def fail (a, b, c):
        print ('Run error:', a, b, c)

    # N.B. The request has to be explicitly encoded, but the response is already implicitly decoded
    jq.ajax ({
        'url':'http://www.transcrypt.org/compile',
        'type': 'POST',
        'data': JSON.stringify (editor.getValue ()),
        'dataType': 'json',
        'contentType': 'application/json',
        'success': success,
        'fail': fail
    })

def mail ():
    def success (result):
        print (result)

    def fail (a, b, c):
        print ('Run error:', a, b, c)

    jq.ajax ({
        'url':'http://www.transcrypt.org/mail',
        'type': 'POST',
        'data': JSON.stringify ([document.getElementById ('mail_address') .value, editor.getValue ()]),
        'dataType': 'json',
        'contentType': 'application/json',
        'success': success,
        'fail': fail
    })

def selectExample ():
    def success (result):
        editor.setValue (result [0])
        turtle.reset ()     # Using old paths
        window.terminate = True
        console.log (result [1])
        eval (result [1])   # Using new paths (so cannot clear old result)

    def fail (a, b, c):
        print ('Select example error:', a, b, c)

    selector = document.getElementById ('select_example')

    jq.ajax ({
        'url':'http://www.transcrypt.org/example',
        'type': 'POST',
        'data': JSON.stringify (selector.options [selector.selectedIndex] .value),
        'dataType': 'json',
        'contentType': 'application/json',
        'success': success,
        'fail': fail
    })

selectExample ()

This is the way it's done at:

http://www.transcrypt.org/live/turtle_site/turtle_site.html

[EDIT]

(in response to comment of OP)

Indeed any ordinary JavaScript object can instantiated this way. Note that in special cases you can always interject a piece of literal JS code, as described in:

http://www.transcrypt.org/docs/html/special_facilities.html#inserting-literal-javascript-pragma-js-and-include

As for the available libs, Transcrypt is designed to use any JS lib directly, since JS libs tend to be focused on functionality that is relevant to the client/browser.

Nevertheless the number of available standard libs is growing. Currently available are:

• cmath
• datetime
• inspect
• itertools
• logging
• math
• random (partially)
• re (almost complete)
• time
• turtle (almost complete)
• warnings

Apart from that there's a port of a small but useful part of Numpy as described in:

http://www.transcrypt.org/numscrypt/docs/html/supported_constructs.html

It is available at:

https://github.com/QQuick/Numscrypt