can I display custom javascript in streamlit web app

Digging in Google I found:

You can add HTML using

import streamlit as st

st.markdown(html_string, unsafe_allow_html=True)

but this can't add JavaScript.

Forum: How to render already prepared html code with Streamlit?

You can add HTML and JavaScript using

import streamlit.components.v1 as components

components.html(html_string)

but this puts it in <iframe>

Doc: Components API reference

Minimal working example

import streamlit as st
import streamlit.components.v1 as components

html_string = '''
<h1>HTML string in RED</h1>

<script language="javascript">
  document.querySelector("h1").style.color = "red";
  console.log("Streamlit runs JavaScript");
  alert("Streamlit runs JavaScript");
</script>
'''

components.html(html_string)  # JavaScript works

st.markdown(html_string, unsafe_allow_html=True)  # JavaScript doesn't work

To put directly HTML with JavaScript you would need to build Component but it seems more complex method which may need code in TypeScript.

See videos in doc: Create a Streamlit Component