eslint/lib/rules/default-case-last.js

An AST-based pattern checker for JavaScript.

/**
 * @fileoverview Rule to enforce `default` clauses in `switch` statements to be last
 * @author Milos Djermanovic
 */

"use strict";

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

/** @type {import('../shared/types').Rule} */
module.exports = {
	meta: {
		type: "suggestion",

		docs: {
			description:
				"Enforce `default` clauses in `switch` statements to be last",
			recommended: false,
			url: "https://eslint.org/docs/latest/rules/default-case-last",
		},

		schema: [],

		messages: {
			notLast: "Default clause should be the last clause.",
		},
	},

	create(context) {
		return {
			SwitchStatement(node) {
				const cases = node.cases,
					indexOfDefault = cases.findIndex(c => c.test === null);

				if (
					indexOfDefault !== -1 &&
					indexOfDefault !== cases.length - 1
				) {
					const defaultClause = cases[indexOfDefault];

					context.report({
						node: defaultClause,
						messageId: "notLast",
					});
				}
			},
		};
	},
};