This will run each of the three parsers on the source code of jQuery 1.6.4 and CodeMirror 3.0b1 for two seconds, and show a table indicating the number of lines parsed per second. Note that UglifyJS always stores location data, and is thus not fairly compared by the benchmark without location data.
Also note that having the developer tools open in Chrome, or Firebug in Firefox heavily influences the numbers you get. In Chrome, the effect even lingers (in the tab) after you close the developer tools. Load in a fresh tab to get (halfway) stable numbers.