[英]Functional programming and local function state assignments
我最近将代码转换为我认为至少部分是功能性javascript。 这是一个Web表单验证过程。 在流程的每个步骤中,功能都会执行自己的验证层,并在将数据传递给下一个功能之前对其进行修改。
1)我的第一个问题是...下面的代码可以至少被认为是“部分”功能吗?
您会注意到,在requiredFields中,我创建了两个Assign ...状态。 它们是该函数的局部函数,并且该函数没有外部副作用。
2)在函数式编程范式的背景下,这种本地分配是不好的做法吗? 这被认为是“局部副作用”吗?
这是模型:
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
这是验证系统:
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
}
3)如果您看到改进此代码的方法,我将不胜感激地看到仍然可以使用lodash可以提供更好的功能重构。
就像上面的评论所建议的那样,特定的代码审查可能不是SO的主题,而是要回答您问题的一般部分:是的,从外部看,没有外部可见副作用的功能可以视为“功能”-说“行为功能”-即使它内部使用分配。
这里可能的问题是如何验证副作用确实仅是内部的,而从外部看不到。
另一个从理论上讲有趣的事实是,存在一些具有行为功能的功能,但只能通过(内部)分配来实现。 请参阅该论文以获取更多详细信息(如果您无法访问ACM数字图书馆中的论文,请尝试在网上搜索该论文的标题和/或作者)。
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