CS50W – Lecture 5 – JavaScript

This is CS50W, CS50’s Web Programming with Python and JavaScript. Register for free at https://cs50.edx.org/web. Slides and …


  1. lmao everytime you do something and in my head im like "but what about? …." you immediately answer my question. u read my mind

  2. Great stuff! Just wondering why CS50W teaches Django instead of Node since it teaches JavaScript anyway and Node seems more widely used than Django to me?

  3. Anyone else getting a JSON error when trying to connect to the currency exchange API? I think it's asking for an access key and Brian hasn't talked about it.

  4. Wowwww! I am so glad to have come across your channel. I really enjoy your tutorials. It's incredibly informative, unique and easy to understand. You have such an interesting style of teaching that really works with me. I appreciate the way you go through all the different ideas more closely to make sure we got them. I am confident that whoever (luckily) stumbles upon your tutorial video will learn a lot. I can't thank you enough. Merci Monsieur, vous êtes l'un des meilleurs tuteurs que j'ai jamais rencontré !

  5. for those who want to add variables more easily to a print or alert statement in javascript or python, you can use the concatenator like so instead of string formatting which i find really confusing in comparison:

    26:05 alert('Count is now at ' + counter)

    for python: print("This is how it works", variable, "yes it really does work")

    note: i knew this from java and i just tried it out in python and javascript and it works perfectly fine although it's a bit different in python 🙂

  6. I am completely speechless, the way Brian is teaching. I believe he is an awesome teacher, presenter, and what not. Thank you so much Brian for all this content. I know thank you is not an enough to express my feelings 😊😊 Awesome..Awesome..Awesome..

  7. I love this lecture, and I am a Javascript beginner too. However, I think that is not a good habit to call the opetator "=" as "equal" when you declare a new variable because this way of thinking will cause you so much trouble once digging deeper into Javascript.

  8. Glad to see such excitement and dedication towards teaching. Thats why institutions like Harvard Has given biggest tech Giants in the world😇

  9. Gosh I be kicking myself had I bought into a coding camp. Finding Brian's lecture while searching on google for the answer to how to JavaScript! Harvard EDX free classes are the best!

  10. Why I get undefinied my li on ul after user click on submit? this is my line

    <!DOCTYPE html>

    <html lang="es">




    document.addEventListener('DOMContentLoaded', function() {

    document.querySelector('form').onsubmit = () => {

    const task = document.querySelector('#tasks').value;

    const li = document.createElement('li');

    li.innerHTML = task;


    // Stop form from submitting

    return false;







    <ul id="tasks">



    <input id="task" placeholder="Nueva Tarea" type="text">

    <input type="submit">




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