Published: Modified: V1
node.js

The acorn javaScript parser

For some projects it might be required to parse javaScript, often doing so might be a task that is done my a javaScript engine, but sometimes on might want to parse javaScript with javaScript. A popular and well know project for doing just that is acorn.

Getting started

Just like any other node.js project I just created a new folder, did an npm init, and installed the latest version of acorn. As of this writing the latest version of acorn is 5.3.0.

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$ mkdir test_acorn
$ cd test_acorn
$ npm init
$ npm install acorn@5.3.0 -- save
$ mkdir demos

I then also made a demos folder, and made my first demo called basic.js. It is a usual practice of mine to start out with a demo like that when trying out a project of any kind.

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let acorn = require('acorn'),
 
node = acorn.parse('var n = 42;');
 
console.log(node);

When calling this script from the command line I end up getting this:

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Node {
  type: 'Program',
  start: 0,
  end: 11,
  body:
   [ Node {
       type: 'VariableDeclaration',
       start: 0,
       end: 11,
       declarations: [Array],
       kind: 'var' } ],
  sourceType: 'script' }

So acorn will give me an array of objects in a body property that is all the content of my javaScript, broken down into objects that give me useful info like the start, and end character position.