eslint/lib/rules/default-param-last.js

   1 /**
   2  * @fileoverview enforce default parameters to be last
   3  * @author Chiawen Chen
   4  */
   5
   6 "use strict";
   7
   8 /** @type {import('../shared/types').Rule} */
   9 module.exports = {
  10     meta: {
  11         type: "suggestion",
  12
  13         docs: {
  14             description: "enforce default parameters to be last",
  15             recommended: false,
  16             url: "https://eslint.org/docs/rules/default-param-last"
  17         },
  18
  19         schema: [],
  20
  21         messages: {
  22             shouldBeLast: "Default parameters should be last."
  23         }
  24     },
  25
  26     create(context) {
  27
  28         /**
  29          * Handler for function contexts.
  30          * @param {ASTNode} node function node
  31          * @returns {void}
  32          */
  33         function handleFunction(node) {
  34             let hasSeenPlainParam = false;
  35
  36             for (let i = node.params.length - 1; i >= 0; i -= 1) {
  37                 const param = node.params[i];
  38
  39                 if (
  40                     param.type !== "AssignmentPattern" &&
  41                     param.type !== "RestElement"
  42                 ) {
  43                     hasSeenPlainParam = true;
  44                     continue;
  45                 }
  46
  47                 if (hasSeenPlainParam && param.type === "AssignmentPattern") {
  48                     context.report({
  49                         node: param,
  50                         messageId: "shouldBeLast"
  51                     });
  52                 }
  53             }
  54         }
  55
  56         return {
  57             FunctionDeclaration: handleFunction,
  58             FunctionExpression: handleFunction,
  59             ArrowFunctionExpression: handleFunction
  60         };
  61     }
  62 };