eslevels

ECMAScript scope levels analyzer based on esprima toolbox

EsLevels

ECMAScript scope levels analyzer based on escope library. The original purpose of this library is to enable scope context coloring in javascript editors (for SublimeText in first order).

The library has only one method levels(syntax, options). It requires the use of a javascript's Mozilla Parser AST argument that can be obtained from such parsers as esprima (acorn parser has different "range" format). The leavels method returns an array of tuples. Each tuple contains 3 numbers:

  • nesting level number &mdash The Integer : -1 for implicit global variables, deeper scopes have higher numbers 0,1,2,...
  • a level's starting position
  • a level's end position

Eslevels runs on many popular web browsers, as well as other ECMAScript platforms such as V8 and Node.js.

Eslevels library is only a single file that you can grab directly from repository, or use npm or bower package managers

Npm:

$> npm install eslevels

, or you could clone a library source code with examples

$> git clone https://github.com/mazurov/eslevels.git
$> cd eslevels
$> npm install

Bower:

$> bower install eslevels

Basic usage: var levels = eslevels.levels(syntax, options)

How to get syntax is described at esprima documentation in details.

options is a dictionary and so far only one option is available:

  • mode — The String control what javascript constructions should be marked. Available values:
    • "full" — (default) Mark a whole source code (white spaces, operators, all keywords,...)
      • "mini" — Mark only important scope-related constructions (identifiers, function and catch keywords)

You can understand the meaning of mode option from the pictures below:

  • "full" mode:

  • "mini" mode:

Open example/browser/index.html in your browser. You will see scope colorizing example.

You need to include 4 scripts:

<script type="text/javascript" src="esprima.js"></script>
<script type="text/javascript" src="estraverse.js"></script>
<script type="text/javascript" src="escope.js"></script>
<script type="text/javascript" src="eslevels.js"></script>

Then parse source code and obtain levels information:

var syntax = esprima.parse(code, {range: true});
var levels = eslevels.levels(syntax);
console.log(levels);

Clone the library source code (described in install section) and run an example:

$> node examples/nodejs/app.js example/nodejs/example.js

In console you will see an ouput of levels function runned on example/nodejs/example.js file.

Something like this:

[ [ 0, 0, 14 ],
  [ -1, 15, 16 ],
  [ 0, 17, 23 ],
  [ 1, 24, 32 ],
  [ 0, 33, 38 ],
  [ 1, 39, 108 ],
  [ 2, 109, 131 ],
  [ 1, 132, 135 ],
  [ 2, 136, 137 ],
  [ 1, 138, 141 ],
  [ 2, 142, 151 ],
  [ 1, 152, 162 ],
  [ 2, 163, 171 ],
  [ 1, 172, 177 ],
  [ 2, 178, 212 ],
  [ 1, 213, 218 ],
  [ 2, 219, 221 ],
  [ 1, 222, 227 ],
  [ 2, 228, 230 ],
  [ 0, 231, 234 ],
  [ 2, 235, 268 ],
  [ 1, 269, 271 ] ]
  • Yusuke Suzuki (twitter: @Constellation) and other contributors of escope library.