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 module.exports = {
  14     meta: {
  15         type: "suggestion",
  16
  17         docs: {
  18             description: "disallow `null` comparisons without type-checking operators",
  19             recommended: false,
  20             url: "https://eslint.org/docs/rules/no-eq-null"
  21         },
  22
  23         schema: [],
  24
  25         messages: {
  26             unexpected: "Use '===' to compare with null."
  27         }
  28     },
  29
  30     create(context) {
  31
  32         return {
  33
  34             BinaryExpression(node) {
  35                 const badOperator = node.operator === "==" || node.operator === "!=";
  36
  37                 if (node.right.type === "Literal" && node.right.raw === "null" && badOperator ||
  38                         node.left.type === "Literal" && node.left.raw === "null" && badOperator) {
  39                     context.report({ node, messageId: "unexpected" });
  40                 }
  41             }
  42         };
  43
  44     }
  45 };