D3.js - Help me to properly scale y-axis to suit dynamic chart data. (Must have experience with D3 JS library for Data-Driven Charts)

I have a rough chart in d3.js. It works, but not quite. The problem is that y axis is not properly scaled to suit. I would like a quote for a simple tweak to fix it. Then, if we communicate well, I would like the script rewritten, in a subsequent job. (At present, there are 3 x 'sections' to produce 3 grouped sets of bars. But I want to integrate these 3 x 'sections', into one section that iterate depending on how many names (maps) are in the list passed to the script.) I need you to use Version 4.13.0. d3.js. The existing graph looks as attached below (ignore the table, that is not generated by this script). The script takes in a list that looks like [{ 'name': 'Brian Epstein', 'val1': 0, 'val2': 0, 'val3': 33 }, { 'name': 'John Lennon', 'val1': 2, 'val2': 10, 'val3': 15 }, { 'name': 'Yoko Ono', 'val1': 1, 'val2': 9, 'val3': 15 }] - Those values might be as low as 1 or 2, or go as high as around say 500. Any other questions, just ask.