函数式编程和局部函数状态分配

我最近将一段代码转换为我认为至少部分是函数式javascript。这是一个web表单验证过程。在过程的每一步，函数执行自己的验证层，并在将数据传递给下一个函数之前修改数据。

你会注意到在requiredFields中我创建了两个赋值…州。它们是函数的局部，函数没有外部副作用....

2)在函数式编程范式的背景下，这种局部分配是不好的实践吗?这被认为是"局部副作用"吗?

模型如下:

function linkmodel() {
    return {
        title: { 
            content: undefined,
            validation: {
                type: "string",
                required: true,
                minLength: 1,
                maxLength: 3,
                validationErrorMessage: "Your title must be a valid string between 1 and 35 characters"
            }
        },
        email: {
            content: undefined,
            validation: {
                type: "email",
                required: true,
                minLength: 1,
                maxLength: 60,
                validationErrorMessage: "Your email must be between 1 and 50 characters"
            }
        },

        link: {
            content: undefined,
            validation: {
                type: "url",
                required: true,
                minLength: 1,
                maxLength: 500,
                validationErrorMessage: "Your link name must be a valid email between 1 and 50 characters"
            }
        },
        description: {
            content: undefined
        }
    }
}

export default linkmodel

验证系统如下:

app.post( "/", function( req, res ) {
  let form = new forms.IncomingForm()
  form.parse( req, function( err, fields, files ) {
    // Lodash launching the function flow
    let errorMessageBag = _.flow( objectWithFieldsToValidate,
                                  requiredFields,
                                  stringLengthValidationCheck,
                                  emailValidation )
    let result = errorMessageBag(fields, linkmodel()) // That's the end result
    console.log( "result", result ) 
  })

  // Return object containing all fields to validate and their criterias
  function objectWithFieldsToValidate( fields, model ) {
    // Remove all model fields that have no validation criteria in model. Description is one of those.
    let modelFieldsToValidate = _.pickBy( model, function( value, key ) { return value.validation !== undefined })
    // Remove from form field any entry that doesn't have a corresponding key in model
    let formFieldsToValidate = _.pick( fields, Object.keys( modelFieldsToValidate ) )
    _.forOwn( modelFieldsToValidate, function( value1, key1 ) {
      _.forOwn( formFieldsToValidate, function( value, key ) {
        if ( key1 === key ) {
          modelFieldsToValidate[ key ].content = value
        }
      })
    })
    return modelFieldsToValidate
  }
  // Take care of required fields
  function requiredFields( objectWithFieldsToValidate ) {
    let okField = {}
    let errors = {}
    // error: field required but empty: add it to errors literal object
    _.forOwn( objectWithFieldsToValidate, function( value, key ) {
      if ( objectWithFieldsToValidate[ key ].validation.required === true && objectWithFieldsToValidate[ key ].content === "" ) {
        errors[ key ] = objectWithFieldsToValidate[ key ].validation.validationErrorMessage
      } else {
        // no error: add field to litteral okField
        okField[ key ] = value
      }
    })
    return ( { "okField": okField, "errors": errors })
  }

  function stringLengthValidationCheck( requiredFields ) {
    let validatedFields = requiredFields
    _.forOwn( validatedFields.okField, function( value, key ) {
      // Error: field length is not valid
      if ( !validator.isLength( value[ "content" ],
        { min: value[ "validation" ].minLength, max: value[ "validation" ].maxLength }
      ) ) {
        // Add error message to errors errors literal object
        validatedFields[ "errors" ][ key ] = value[ "validation" ].validationErrorMessage
        // Remove problematic field from okFields
        delete validatedFields[ "okField" ][ key ]
      }
    })
    return validatedFields
  }

  function emailValidation( stringLengthValidationCheck ) {
    let validatedFields = stringLengthValidationCheck
    _.forOwn( validatedFields.okField, function( value, key ) {
      // Error
      if ( value["validation"]["type"] === "email" && !validator.isEmail( value[ "content" ])) {
        // Add error message to errors
        validatedFields[ "errors" ][ key ] = value[ "validation" ].validationErrorMessage
        // Remove problematic field from okFields
        delete validatedFields[ "okField" ][ key ]
      }
    })
    return validatedFields
  }