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: / proc / self / root / usr / share / nodejs / eslint / lib / rules /
Filename : no-compare-neg-zero.js
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/**
 * @fileoverview The rule should warn against code that tries to compare against -0.
 * @author Aladdin-ADD <hh_2013@foxmail.com>
 */
"use strict";

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

module.exports = {
    meta: {
        type: "problem",

        docs: {
            description: "disallow comparing against -0",
            category: "Possible Errors",
            recommended: true,
            url: "https://eslint.org/docs/rules/no-compare-neg-zero"
        },

        fixable: null,
        schema: [],

        messages: {
            unexpected: "Do not use the '{{operator}}' operator to compare against -0."
        }
    },

    create(context) {

        //--------------------------------------------------------------------------
        // Helpers
        //--------------------------------------------------------------------------

        /**
         * Checks a given node is -0
         *
         * @param {ASTNode} node - A node to check.
         * @returns {boolean} `true` if the node is -0.
         */
        function isNegZero(node) {
            return node.type === "UnaryExpression" && node.operator === "-" && node.argument.type === "Literal" && node.argument.value === 0;
        }
        const OPERATORS_TO_CHECK = new Set([">", ">=", "<", "<=", "==", "===", "!=", "!=="]);

        return {
            BinaryExpression(node) {
                if (OPERATORS_TO_CHECK.has(node.operator)) {
                    if (isNegZero(node.left) || isNegZero(node.right)) {
                        context.report({
                            node,
                            messageId: "unexpected",
                            data: { operator: node.operator }
                        });
                    }
                }
            }
        };
    }
};