typhonjs-ast-walker

!typhonjs-ast-walker



Provides a simple Javascript AST traversal utility that traverses all nodes / children regardless of type.

A single method traverse takes an AST object or array of nodes and a callback object which may contain two methods enterNode and exitNode which are invoked with the current node and the parent node respectively when entering and exiting a given node during traversal.

enterNode may return a array of strings which provide a set of children keys to ignore or null to skip traversing children keys entirely.

To install typhonjs-ast-walker provide this entry in package.json:
``
{
...
"dependencies": {
"typhonjs-ast-walker": "^0.2.0"
}
}
`

A simple example follows:
`
import walker from 'typhonjs-ast-walker';

const ast = .... // An AST tree.

walker.traverse(ast,
{
enterNode: (node, parent) =>
{
console.log(walker - enterNode: ${node.type});

// Optional return statement to ignore specific children keys.
// return node.type === 'ClassBody' ? ['body'] : undefined;

// Optional return statement to ignore specific children keys or skip traversal entirely.
// return node.type === 'ClassBody' ? null : undefined;
},

exitNode: (node, parent) =>
{
console.log(walker - exitNode: ${node.type});
}
});

`

Support for typhonjs-plugin-manager is also available and
when loading typhonjs-ast-walker as a plugin it will automatically register event bindings on the plugin eventbus
with these event categories:

ast:walker:traverse - invokes traverse of the default walker.

Example typhonjs-plugin-manager usage:
`
import PluginManager from 'typhonjs-plugin-manager';
import eventbus from 'backbone-esnext-eventbus';

const pluginManager = new PluginManager({ eventbus });

pluginManager.add({ name: typhonjs-ast-walker });

// This will automatically wire up typhonjs-ast-walker to the eventbus.

eventbus.trigger('ast:walker:traverse, ast,
{
enterNode: (node, parent) =>
{
console.log(walker - enterNode: ${node.type});
},

exitNode: (node, parent) =>
{
console.log(walker - exitNode: ${node.type});
}
});
``