ast-utils

Utility library to manipulate ASTs

Install

$ npm install --save ast-utils

Usage

const astUtils = require('ast-utils');

API

astUtils.isStaticRequire(node)

Checks whether node is a call to CommonJS's require function.

Returns true if and only if:

• node is a CallExpression
• node's callee is an Identifier named require
• node has exactly 1 Literal argument whose value is a string

Example:

require('lodash');
// => true
require(foo);
// => false
foo('lodash');
// => false

Usage example (in the context of an ESLint rule):

function create(context) {
	return {
		CallExpression(node) {
			if (astUtils.isStaticRequire(node)) {
				context.report({
					node: node,
					message: 'Use import syntax rather than `require`'
				});
			}
		}
	};
}

astUtils.getRequireSource(node)

Gets the source of a require() call. If node is not a require call (in the definition of isStaticRequire), it will return undefined.

Example:

require('lodash');
// => 'lodash'
require('./foo');
// => './foo'

Usage example (in the context of an ESLint rule):

function create(context) {
	return {
		CallExpression(node) {
			if (astUtils.isStaticRequire(node) && astUtils.getRequireSource(node) === 'underscore') {
				context.report({
					node: node,
					message: 'Use `lodash` instead of `underscore`'
				});
			}
		}
	};
}

astUtils.containsIdentifier(name, node)

Checks if there is a reference to a variable named name inside of node.

Returns true if and only if:

• There is an Identifier named name inside of node
• That Identifier is a variable (i.e. not a static property name for instance)
• That Identifier does not reference a different variable named name introduced in a sub-scope of node.

Example:

foo(a);
// containsIdentifier('a', node) // => true
// containsIdentifier('b', node) // => true

function foo(fn) {
	return function(a) {
		return fn(a);
	};
}
// containsIdentifier('a', node) // => false

Usage example (in the context of an ESLint rule):

function create(context) {
	return {
		FunctionDeclaration(node) {
			node.params.forEach(param => {
				if (param.type === 'Identifier' && !astUtils.containsIdentifier(param.name, node.body)) {
					context.report({
						node: node,
						message: `${name} is never used`
					});
				}
			});
		}
	};
}

astUtils.someContainIdentifier(name, nodes)

Checks if there is a reference to a variable named name inside any node of the nodes array. Will return false if nodes is not an array. This is a shorthand version of containsIdentifier that works for arrays. The following are equivalent:

[node1, node2, node3].some(node => astUtils.containsIdentifier('a', node));
// equivalent to
astUtils.someContainIdentifier('a', [node1, node2, node3]);

License

MIT © Jeroen Engels