eslint/lib/rules/no-compare-neg-zero.js

   1 /**
   2  * @fileoverview The rule should warn against code that tries to compare against -0.
   3  * @author Aladdin-ADD <hh_2013@foxmail.com>
   4  */
   5 "use strict";
   6
   7 //------------------------------------------------------------------------------
   8 // Rule Definition
   9 //------------------------------------------------------------------------------
  10
  11 /** @type {import('../shared/types').Rule} */
  12 module.exports = {
  13     meta: {
  14         type: "problem",
  15
  16         docs: {
  17             description: "Disallow comparing against -0",
  18             recommended: true,
  19             url: "https://eslint.org/docs/rules/no-compare-neg-zero"
  20         },
  21
  22         fixable: null,
  23         schema: [],
  24
  25         messages: {
  26             unexpected: "Do not use the '{{operator}}' operator to compare against -0."
  27         }
  28     },
  29
  30     create(context) {
  31
  32         //--------------------------------------------------------------------------
  33         // Helpers
  34         //--------------------------------------------------------------------------
  35
  36         /**
  37          * Checks a given node is -0
  38          * @param {ASTNode} node A node to check.
  39          * @returns {boolean} `true` if the node is -0.
  40          */
  41         function isNegZero(node) {
  42             return node.type === "UnaryExpression" && node.operator === "-" && node.argument.type === "Literal" && node.argument.value === 0;
  43         }
  44         const OPERATORS_TO_CHECK = new Set([">", ">=", "<", "<=", "==", "===", "!=", "!=="]);
  45
  46         return {
  47             BinaryExpression(node) {
  48                 if (OPERATORS_TO_CHECK.has(node.operator)) {
  49                     if (isNegZero(node.left) || isNegZero(node.right)) {
  50                         context.report({
  51                             node,
  52                             messageId: "unexpected",
  53                             data: { operator: node.operator }
  54                         });
  55                     }
  56                 }
  57             }
  58         };
  59     }
  60 };