Only comment things that have business logic complexity

Comments are an apology, not a requirement. Good code mostly documents itself.

Bad:

function hashIt(data) {
  // The hash
  let hash = 0;

  // Length of string
  const length = data.length;

  // Loop through every character in data
  for (let i = 0; i < length; i++) {
    // Get character code.
    const char = data.charCodeAt(i);
    // Make the hash
    hash = (hash << 5) - hash + char;
    // Convert to 32-bit integer
    hash &= hash;
  }
}

Good:

function hashIt(data) {
  let hash = 0;
  const length = data.length;

  for (let i = 0; i < length; i++) {
    const char = data.charCodeAt(i);
    hash = (hash << 5) - hash + char;

    // Convert to 32-bit integer
    hash &= hash;
  }
}