Function e_button

static/editor.md/lib/codemirror/lib/codemirror.js:7897–7906

(e)

  function e_target(e) {return e.target || e.srcElement;}
  function e_button(e) {
    var b = e.which;
    if (b == null) {
      if (e.button & 1) b = 1;
      else if (e.button & 2) b = 3;
      else if (e.button & 4) b = 2;
    }
    if (mac && e.ctrlKey && b == 1) b = 3;
    return b;
  }

  // EVENT HANDLING