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node_modules/eslint/lib/rules/guard-for-in.js 2.22 KB
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  /**
   * @fileoverview Rule to flag for-in loops without if statements inside
   * @author Nicholas C. Zakas
   */
  
  "use strict";
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  module.exports = {
      meta: {
          docs: {
              description: "require `for-in` loops to include an `if` statement",
              category: "Best Practices",
              recommended: false,
              url: "https://eslint.org/docs/rules/guard-for-in"
          },
  
          schema: []
      },
  
      create(context) {
  
          return {
  
              ForInStatement(node) {
                  const body = node.body;
  
                  // empty statement
                  if (body.type === "EmptyStatement") {
                      return;
                  }
  
                  // if statement
                  if (body.type === "IfStatement") {
                      return;
                  }
  
                  // empty block
                  if (body.type === "BlockStatement" && body.body.length === 0) {
                      return;
                  }
  
                  // block with just if statement
                  if (body.type === "BlockStatement" && body.body.length === 1 && body.body[0].type === "IfStatement") {
                      return;
                  }
  
                  // block that starts with if statement
                  if (body.type === "BlockStatement" && body.body.length >= 1 && body.body[0].type === "IfStatement") {
                      const i = body.body[0];
  
                      // ... whose consequent is a continue
                      if (i.consequent.type === "ContinueStatement") {
                          return;
                      }
  
                      // ... whose consequent is a block that contains only a continue
                      if (i.consequent.type === "BlockStatement" && i.consequent.body.length === 1 && i.consequent.body[0].type === "ContinueStatement") {
                          return;
                      }
                  }
  
                  context.report({ node, message: "The body of a for-in should be wrapped in an if statement to filter unwanted properties from the prototype." });
              }
          };
  
      }
  };