You have to install CustomJS as well. Then you define a folder in CustomJS’ settings where you put the dailyGantt.js file above (folder relative to your vault root). For testing, you can set the dates in the beginning of the short script to an actual date like so:
let today = "2024-01-23";
let tomorrow = "2024-01-24";
Let me know if it works, because unfortunately it doesn’t for me (I have lots of tasks, but no Gantt is showing up although something is rendered:
Not sure what to make of this. Will be looking into it some more…