eslint-config-chain-able/node_modules/eslint-plugin-no-for-each/lib/rules/no-for-in.js

an opinionated ESLint configuration

module.exports = {
  meta: {
    fixable: 'code',
    docs: {
      description: 'no for in, autofix to normal for loop',
      category: 'Best Practices',
      recommended: false
    },
    schema: [
      {
        enum: ['always', 'never', 'cache-length']
      }
    ]
  },

  create: function(context) {
    var sourceCode = context.getSourceCode()
    var configuration = context.options[0]
    var loopVariableDefinedInBlock = require('../processors/loop-variable-in-block')
    var leftDeclaration = require('../processors/left-declaration')
    var replaceDeclarationIfNeeded = require('../processors/replace-declaration-if-needed')

    return {
      /**
       * @TODO:
       * - [ ] use getOwnPropertyNames() if commented?
       *
       * @tutorial
       * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in
       *
       *
       * @example:
       *  var triangle = {a:1, b:2, c:3};
       *
       *  function ColoredTriangle() {
       *    this.color = "red";
       *  }
       *
       *  ColoredTriangle.prototype = triangle;
       *
       *  var obj = new ColoredTriangle();
       *
       * #1 for (
       *     var
       * #2   prop
       *     in
       * #3   obj
       *     )
       * #4 {
       *  #5   if (obj.hasOwnProperty(prop)) {
       *  #5     console.log("obj." + prop + " = " + obj[prop]);
       *  #5   }
       * #4 }
       *
       * #1 = node
       * #2 = node.left
       * #3 = node.right
       * #4 = node.body
       * #5 = node.body.body
       *
       * @TODO:
       * - [ ] use getOwnPropertyNames() if commented?
       * - [ ] comment a line above like /* eslint-all-props * /
       * -> or /* eslint-own-props * /
       *
       * @NOTE: changed to be named `len`, was:
       * `cacheLengthInLoop = ', ' + varLengthName + ' = ' + variableName + '.length'`
       */
      'ForInStatement': function(node) {
        var declaration = leftDeclaration(node)
        var obj = node.right.name

        var code = ''
        var variableName = declaration + 'Keys'
        var varLengthName = 'len' // variableName + 'Len'
        var cacheLengthInLoop = ', len = ' + variableName + '.length'

        var bodyTxt = sourceCode.getText(node.body)
        var body = replaceDeclarationIfNeeded(bodyTxt, declaration, obj, variableName)
        var bodySplit = loopVariableDefinedInBlock(variableName, declaration, obj, body, true)

        context.report({
          node: node,
          message: 'no for in loop',
          fix: function(fixer) {
            code += 'let ' + variableName + ' = Object.keys(' + obj + ');\n'
            code += 'for (let i = 0' + cacheLengthInLoop + '; i < ' + varLengthName + '; i++) ' + bodySplit

            var fixed = fixer.replaceTextRange([node.start, node.end], code)
            console.log(fixed.text)
            return fixed
          }
        }) // report
      }

    }
  }
}