Redraw a Google Chart from User Input

Validate numeric input before redrawing

Convert form values to numbers and reject non-finite values before rebuilding the chart data.

function readNumber(id) {
  const value = Number(document.getElementById(id).value);
  return Number.isFinite(value) ? value : 0;
}

const php = readNumber('php');
const mysql = readNumber('mysql');

Current example first; the original chart examples below are retained and cleaned up for continued learning.