New: no-instanceof-array rule

README.md

@@ -27,6 +27,7 @@ npm install --save-dev eslint eslint-plugin-mysticatea
     "rules": {
         "mysticatea/arrow-parens": "error",
         "mysticatea/block-scoped-var": "error",
+        "mysticatea/no-instanceof-array": "error",
         "mysticatea/no-instanceof-wrapper": "error",
         "mysticatea/no-literal-call": "error",
         "mysticatea/no-this-in-static": "error",
@@ -43,6 +44,7 @@ npm install --save-dev eslint eslint-plugin-mysticatea
 
 - [arrow-parens](docs/rules/arrow-parens.md) - Enforce parens of argument lists (excludes too redundant parens) (fixable).
 - [block-scoped-var](docs/rules/block-scoped-var.md) - The complete emulation of block-scoping for `var`.
+- [no-instanceof-array](docs/rules/no-instanceof-array.md) - Disallow 'instanceof' for Array.
 - [no-instanceof-wrapper](docs/rules/no-instanceof-wrapper.md) - Disallow 'instanceof' for wrapper objects.
 - [no-literal-call](docs/rules/no-literal-call.md) - Disallow a call of a literal.
 - [no-this-in-static](docs/rules/no-this-in-static.md) - Disallow `this`/`super` in static methods.

docs/rules/no-instanceof-array.md

@@ -0,0 +1,19 @@
+# Disallow 'instanceof' for Array (no-instanceof-array)
+
+## Rule Details
+
+Examples of **incorrect** code for this rule:
+
+```js
+/*eslint no-instanceof-array: "error"*/
+
+x instanceof Array
+```
+
+Examples of **correct** code for this rule:
+
+```js
+/*eslint no-instanceof-array: "error"*/
+
+Array.isArray(x)
+```

lib/rules/no-instanceof-array.js

@@ -0,0 +1,72 @@
+/**
+ * @author Toru Nagashima
+ * @copyright 2016 Toru Nagashima. All rights reserved.
+ * See LICENSE file in root directory for full license.
+ */
+"use strict"
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow 'instanceof' for Array",
+            category: "Best Practices",
+        },
+        fixable: true,
+        schema: [],
+    },
+
+    create(context) {
+        const sourceCode = context.getSourceCode()
+
+        /**
+         * Checks whether the given node is RHS of instanceof.
+         *
+         * @param {ASTNode} node - The node to check.
+         * @returns {boolean} `true` if the node is RHS of instanceof.
+         */
+        function isRhsOfInstanceof(node) {
+            return (
+                node.parent.type === "BinaryExpression" &&
+                node.parent.operator === "instanceof" &&
+                node.parent.right === node
+            )
+        }
+
+        return {
+            "Program:exit"() {
+                const globalScope = context.getScope()
+                const variable = globalScope.set.get("Array")
+
+                // Skip if undefined or shadowed
+                if (variable == null || variable.defs.length > 0) {
+                    return
+                }
+
+                for (const reference of variable.references) {
+                    const id = reference.identifier
+                    const node = id.parent
+
+                    // Skip if it's not instanceof
+                    if (!isRhsOfInstanceof(id)) {
+                        continue
+                    }
+
+                    // Report
+                    context.report({
+                        node,
+                        loc: node.loc,
+                        message: "Unexpected 'instanceof' operator. Use 'Array.isArray' instead.",
+                        fix: (fixer) => fixer.replaceText(
+                            node,
+                            `Array.isArray(${sourceCode.getText(node.left)})`
+                        ),
+                    })
+                }
+            },
+        }
+    },
+}

tests/lib/rules/no-instanceof-array.js

@@ -0,0 +1,34 @@
+/**
+ * @author Toru Nagashima
+ * @copyright 2016 Toru Nagashima. All rights reserved.
+ * See LICENSE file in root directory for full license.
+ */
+"use strict"
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const RuleTester = require("eslint").RuleTester
+const rule = require("../../../lib/rules/no-instanceof-array")
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+const tester = new RuleTester()
+
+tester.run("no-instanceof-array", rule, {
+    valid: [
+        "Array",
+        "Array.isArray(x)",
+        "function foo(Array) { x instanceof Array }",
+    ],
+    invalid: [
+        {
+            code: "x instanceof Array",
+            output: "Array.isArray(x)",
+            errors: ["Unexpected 'instanceof' operator. Use 'Array.isArray' instead."],
+        },
+    ],
+})