JavaScript AST manipulation

ast_manipulation.js

#!/usr/bin/env node

let { generate } = require("escodegen");
let jsx = require("acorn-jsx");
let acorn = require("acorn");
let { strictEqual: assertSame } = require("assert");

let JSXParser = acorn.Parser.extend(jsx());

let ast = JSXParser.parse(`<Card title={123}>
	lorem ipsum
	{9.87}
</Card>`);
let root = ast.body[0].expression;
validateNode(root, "JSXElement"); // sanity check
console.error(root);

console.error("\n----\n");

// rewrite node in place -- FIXME: discards `start`, `end`
Object.keys(root).forEach(key => {
	delete root[key]; // XXX: crude?
});
Object.assign(root, $array(
		$invocation("Card", $object({ title: $literal(123) }),
				$literal("lorem ipsum"), $literal(9.87)),
		$literal(false),
		$literal(null)
));
let code = generate(ast);
console.error(`<pre>\n${code}\n</pre>`);

function $invocation(functionName, ...args) {
	return {
		type: "CallExpression",
		callee: {
			type: "Identifier",
			name: functionName
		},
		arguments: args
	};
}

function $array(...elements) {
	return {
		type: "ArrayExpression",
		elements
	};
}

function $object(obj) {
	return {
		type: "ObjectExpression",
		properties: Object.entries(obj).map(([key, value]) => ({
			type: "Property",
			kind: "init", // XXX: ?
			method: false,
			shorthand: false,
			computed: false,
			key: {
				type: "Identifier",
				name: key
			},
			value
		}))
	};
}

function $literal(value) {
	return {
		type: "Literal",
		value,
		raw: JSON.stringify(value) // XXX: unnecessary?
	};
}

function validateNode({ type }, expected) {
	assertSame(type, expected, `expected \`${expected}\`, got \`${type}\``);
}