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app_vue/node_modules/eslint/lib/rules/use-isnan.js

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+/**
+ * @fileoverview Rule to flag comparisons to the value NaN
+ * @author James Allardice
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+/**
+ * Determines if the given node is a NaN `Identifier` node.
+ * @param {ASTNode|null} node The node to check.
+ * @returns {boolean} `true` if the node is 'NaN' identifier.
+ */
+function isNaNIdentifier(node) {
+    return Boolean(node) && (
+        astUtils.isSpecificId(node, "NaN") ||
+        astUtils.isSpecificMemberAccess(node, "Number", "NaN")
+    );
+}
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        type: "problem",
+
+        docs: {
+            description: "require calls to `isNaN()` when checking for `NaN`",
+            category: "Possible Errors",
+            recommended: true,
+            url: "https://eslint.org/docs/rules/use-isnan"
+        },
+
+        schema: [
+            {
+                type: "object",
+                properties: {
+                    enforceForSwitchCase: {
+                        type: "boolean",
+                        default: true
+                    },
+                    enforceForIndexOf: {
+                        type: "boolean",
+                        default: false
+                    }
+                },
+                additionalProperties: false
+            }
+        ],
+
+        messages: {
+            comparisonWithNaN: "Use the isNaN function to compare with NaN.",
+            switchNaN: "'switch(NaN)' can never match a case clause. Use Number.isNaN instead of the switch.",
+            caseNaN: "'case NaN' can never match. Use Number.isNaN before the switch.",
+            indexOfNaN: "Array prototype method '{{ methodName }}' cannot find NaN."
+        }
+    },
+
+    create(context) {
+
+        const enforceForSwitchCase = !context.options[0] || context.options[0].enforceForSwitchCase;
+        const enforceForIndexOf = context.options[0] && context.options[0].enforceForIndexOf;
+
+        /**
+         * Checks the given `BinaryExpression` node for `foo === NaN` and other comparisons.
+         * @param {ASTNode} node The node to check.
+         * @returns {void}
+         */
+        function checkBinaryExpression(node) {
+            if (
+                /^(?:[<>]|[!=]=)=?$/u.test(node.operator) &&
+                (isNaNIdentifier(node.left) || isNaNIdentifier(node.right))
+            ) {
+                context.report({ node, messageId: "comparisonWithNaN" });
+            }
+        }
+
+        /**
+         * Checks the discriminant and all case clauses of the given `SwitchStatement` node for `switch(NaN)` and `case NaN:`
+         * @param {ASTNode} node The node to check.
+         * @returns {void}
+         */
+        function checkSwitchStatement(node) {
+            if (isNaNIdentifier(node.discriminant)) {
+                context.report({ node, messageId: "switchNaN" });
+            }
+
+            for (const switchCase of node.cases) {
+                if (isNaNIdentifier(switchCase.test)) {
+                    context.report({ node: switchCase, messageId: "caseNaN" });
+                }
+            }
+        }
+
+        /**
+         * Checks the given `CallExpression` node for `.indexOf(NaN)` and `.lastIndexOf(NaN)`.
+         * @param {ASTNode} node The node to check.
+         * @returns {void}
+         */
+        function checkCallExpression(node) {
+            const callee = astUtils.skipChainExpression(node.callee);
+
+            if (callee.type === "MemberExpression") {
+                const methodName = astUtils.getStaticPropertyName(callee);
+
+                if (
+                    (methodName === "indexOf" || methodName === "lastIndexOf") &&
+                    node.arguments.length === 1 &&
+                    isNaNIdentifier(node.arguments[0])
+                ) {
+                    context.report({ node, messageId: "indexOfNaN", data: { methodName } });
+                }
+            }
+        }
+
+        const listeners = {
+            BinaryExpression: checkBinaryExpression
+        };
+
+        if (enforceForSwitchCase) {
+            listeners.SwitchStatement = checkSwitchStatement;
+        }
+
+        if (enforceForIndexOf) {
+            listeners.CallExpression = checkCallExpression;
+        }
+
+        return listeners;
+    }
+};