How to display the result of a Javascript cell?

Notebook
1

Hi, I have this JS code in a code cell and when it runs nothing happens…

%%js
// Put a zero in for the unknown value
let n1 = 1;
let d1 = 2;
let n2 = 0;
let d2 = 16;

if (n2 === 0) {
  let answer = (d2 * n1) / d1;
  console.log("n2 =", answer);
}

if (d2 === 0) {
  let answer = (n2 * d1) / n1;
  console.log("d2 =", answer);
}

I’m trying to translate that python code that work:

# Put a zero in for the unknown value
n1 = 1
d1 = 2
n2 = 0
d2 = 16

if n2==0:
    answer = d2 * n1 / d1
    print("n2 = ", answer)
    
if d2==0:
    answer = n2 * d1 / n1
    print("d2 = ", answer)

thanks for your help :slight_smile:

2

The code just runs in your browser, so the output is in the browser console.

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If you want the output to be inside a notebook you should install nodejs and a javascript kernel.
I use tslab but since jupyterlab 4 the syntax highlighting does not work anymore.

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image777×453 29 KB

2 Likes
3

Hey @spookster! thank you so much for your answer!
I see, yes I’m getting the correct output in the console.
Now I tried to install tslab following the recommendations from the Github link:

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image838×923 76.9 KB

(I have Python 3.10.6 and node v20.4.0 installed)
but it still doesn’t work:
image
I’m using Jupyter Notebook 7.0
Thank you :slight_smile:

4

the syntax highlighting suggest you are still on the Python kernel.

you need to create a notebook using the javascript kernel or switch the kernel in the top right corner to the javascript kernel.

1 Like
5

@spookster it works! (after restarting the server)
thanks for your help I really appreciate it! have a good one :slight_smile:

2 Likes
6

@spookster I’m getting this error when restarting the server:

image

running the Python 3 (ipykernel) kernel works fine… any idea?

finding this post: Kernel Error: Failed to start a kernel - #3 by Rose_Zhang
it looks like it works when I start the server from the command line but not from the launcher… (on linux mint with jupyter notebook 7.0)

7

add the the folder with npm binaries to your PATH environment variable.

8

Hi @spookster, I have tried different stackoverflow solutions like

export PATH=$PATH:/home/user_name/.nvm/versions/node/v20.4.0/bin

or

image

** with the correct path I get from which node **

but nothing worked so far…
Would you mind telling me the commands?
Thank you

9

this should normally work but I don’t know why it’s not working for you.

you can put the complete path into the .local/share/jupyter/kernels/jslab/kernel.json (and the tslab kernel too while you are at it).

just change

{"argv": ["tslab", "kernel", "--config-path", "{connection_file}", "--js"], "display_name": "JavaScript", "language": "javascript"}

to something like this:

{"argv": ["/path/to/your/tslab/executable/from/which/tslab", "kernel", "--config-path", "{connection_file}", "--js"], "display_name": "JavaScript", "language": "javascript"}