eslint/lib/rules/no-eq-null.js

   1 /**
   2  * @fileoverview Rule to flag comparisons to null without a type-checking
   3  * operator.
   4  * @author Ian Christian Myers
   5  */
   6
   7 "use strict";
   8
   9 //------------------------------------------------------------------------------
  10 // Rule Definition
  11 //------------------------------------------------------------------------------
  12
  13 /** @type {import('../shared/types').Rule} */
  14 module.exports = {
  15     meta: {
  16         type: "suggestion",
  17
  18         docs: {
  19             description: "Disallow `null` comparisons without type-checking operators",
  20             recommended: false,
  21             url: "https://eslint.org/docs/rules/no-eq-null"
  22         },
  23
  24         schema: [],
  25
  26         messages: {
  27             unexpected: "Use '===' to compare with null."
  28         }
  29     },
  30
  31     create(context) {
  32
  33         return {
  34
  35             BinaryExpression(node) {
  36                 const badOperator = node.operator === "==" || node.operator === "!=";
  37
  38                 if (node.right.type === "Literal" && node.right.raw === "null" && badOperator ||
  39                         node.left.type === "Literal" && node.left.raw === "null" && badOperator) {
  40                     context.report({ node, messageId: "unexpected" });
  41                 }
  42             }
  43         };
  44
  45     }
  46 };