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}`);
}
});