Javascript Hello World

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One of the very first programs you can write to make sure your version of Node is working is the "Hello World" program . There are two ways to create the program: in terminal or in your favorite code editor (eg Visual Studio Code, Vim, etc.). Make sure Node is installed on your machine to get started.

1.In your terminal, type node to start Node.

As the terminal should appear after starting Python 3
What the terminal should look like after starting Node.

2. Enter console.log (" Hello World ") into the interpreter and press Enter.

3.Hello World will show the next line ! do not worry if it says "undefined" on the next line. it just means that we do not return anything that or a function.

4. If you also want to create a proof function ! Here & rsquo; how in the terminal:

Vo DVBO BANAU O1MAGHVB6i XLHn9gcFgMxEfBe1tiMBX8G8V2iBzXAyilN5Y9zs0YpRa7xz6zjBxp0FTaCLlGOb1XiJLxvTlxpFFOMBmeLTQvknOi0TcRQOhchTrs5wi function in figure. If you want to run it, type <code>helloWorld ()</code> in the terminal and hit enter. Bonjour Monde! Will return to the console.</p> <h2> Code editor (i.e. Visual Studio code)</h2><ol> <li>Open your favorite editor and create a new file and save it as hello.js.</li><li>In your file, enter console.log (
  • In your terminal, go to the directory / folder where you saved your file. Use cd and ls to navigate from one directory to another.
  • Use the hello.js node to run the file. Hello World should appear on the next line ssiva.
  • If you are using VS Code, the "play" button in the upper right corner will also play the current file and display the output in the lower half of the screen.
  • That’s it ! You have successfully created a simple JavaScript program that shows that your Node environment is working.

    Javascript Hello World JavaScript: Questions

    JSON datetime between Python and JavaScript

    4 answers

    kevin By kevin

    I want to send a datetime.datetime object in serialized form from Python using JSON and de-serialize in JavaScript using JSON. What is the best way to do this?

    403

    Answer #1

    You can add the "default" parameter to json.dumps to handle this:

    date_handler = lambda obj: (
        obj.isoformat()
        if isinstance(obj, (datetime.datetime, datetime.date))
        else None
    )
    json.dumps(datetime.datetime.now(), default=date_handler)
    ""2010-04-20T20:08:21.634121""
    

    Which is ISO 8601 format.

    A more comprehensive default handler function:

    def handler(obj):
        if hasattr(obj, "isoformat"):
            return obj.isoformat()
        elif isinstance(obj, ...):
            return ...
        else:
            raise TypeError, "Object of type %s with value of %s is not JSON serializable" % (type(obj), repr(obj))
    

    Update: Added output of type as well as value.
    Update: Also handle date

    What blocks Ruby, Python to get Javascript V8 speed?

    4 answers

    Are there any Ruby / Python features that are blocking implementation of optimizations (e.g. inline caching) V8 engine has?

    Python is co-developed by Google guys so it shouldn"t be blocked by software patents.

    Or this is rather matter of resources put into the V8 project by Google.

    260

    Answer #1

    What blocks Ruby, Python to get Javascript V8 speed?

    Nothing.

    Well, okay: money. (And time, people, resources, but if you have money, you can buy those.)

    V8 has a team of brilliant, highly-specialized, highly-experienced (and thus highly-paid) engineers working on it, that have decades of experience (I"m talking individually – collectively it"s more like centuries) in creating high-performance execution engines for dynamic OO languages. They are basically the same people who also created the Sun HotSpot JVM (among many others).

    Lars Bak, the lead developer, has been literally working on VMs for 25 years (and all of those VMs have lead up to V8), which is basically his entire (professional) life. Some of the people writing Ruby VMs aren"t even 25 years old.

    Are there any Ruby / Python features that are blocking implementation of optimizations (e.g. inline caching) V8 engine has?

    Given that at least IronRuby, JRuby, MagLev, MacRuby and Rubinius have either monomorphic (IronRuby) or polymorphic inline caching, the answer is obviously no.

    Modern Ruby implementations already do a great deal of optimizations. For example, for certain operations, Rubinius"s Hash class is faster than YARV"s. Now, this doesn"t sound terribly exciting until you realize that Rubinius"s Hash class is implemented in 100% pure Ruby, while YARV"s is implemented in 100% hand-optimized C.

    So, at least in some cases, Rubinius can generate better code than GCC!

    Or this is rather matter of resources put into the V8 project by Google.

    Yes. Not just Google. The lineage of V8"s source code is 25 years old now. The people who are working on V8 also created the Self VM (to this day one of the fastest dynamic OO language execution engines ever created), the Animorphic Smalltalk VM (to this day one of the fastest Smalltalk execution engines ever created), the HotSpot JVM (the fastest JVM ever created, probably the fastest VM period) and OOVM (one of the most efficient Smalltalk VMs ever created).

    In fact, Lars Bak, the lead developer of V8, worked on every single one of those, plus a few others.

    Django Template Variables and Javascript

    4 answers

    When I render a page using the Django template renderer, I can pass in a dictionary variable containing various values to manipulate them in the page using {{ myVar }}.

    Is there a way to access the same variable in Javascript (perhaps using the DOM, I don"t know how Django makes the variables accessible)? I want to be able to lookup details using an AJAX lookup based on the values contained in the variables passed in.

    256

    Answer #1

    The {{variable}} is substituted directly into the HTML. Do a view source; it isn"t a "variable" or anything like it. It"s just rendered text.

    Having said that, you can put this kind of substitution into your JavaScript.

    <script type="text/javascript"> 
       var a = "{{someDjangoVariable}}";
    </script>
    

    This gives you "dynamic" javascript.

    Javascript Hello World log: Questions

    log

    Python"s equivalent of && (logical-and) in an if-statement

    5 answers

    delete By delete

    Here"s my code:

    def front_back(a, b):
      # +++your code here+++
      if len(a) % 2 == 0 && len(b) % 2 == 0:
        return a[:(len(a)/2)] + b[:(len(b)/2)] + a[(len(a)/2):] + b[(len(b)/2):] 
      else:
        #todo! Not yet done. :P
      return
    

    I"m getting an error in the IF conditional.
    What am I doing wrong?

    934

    Answer #1

    You would want and instead of &&.

    934

    Answer #2

    Python uses and and or conditionals.

    i.e.

    if foo == "abc" and bar == "bac" or zoo == "123":
      # do something
    

    log

    How do you get the logical xor of two variables in Python?

    5 answers

    Zach Hirsch By Zach Hirsch

    How do you get the logical xor of two variables in Python?

    For example, I have two variables that I expect to be strings. I want to test that only one of them contains a True value (is not None or the empty string):

    str1 = raw_input("Enter string one:")
    str2 = raw_input("Enter string two:")
    if logical_xor(str1, str2):
        print "ok"
    else:
        print "bad"
    

    The ^ operator seems to be bitwise, and not defined on all objects:

    >>> 1 ^ 1
    0
    >>> 2 ^ 1
    3
    >>> "abc" ^ ""
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    TypeError: unsupported operand type(s) for ^: "str" and "str"
    
    794

    Answer #1

    If you"re already normalizing the inputs to booleans, then != is xor.

    bool(a) != bool(b)
    

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