Reactive statement throws an error once it hits undefined variables. How to prevent it? - undefined

just playing around with Svelte. And I have noticed that when the reactive statement ($) is being calculated, it will throw an error when one of the depending variables is undefined.
While this behaviour is correct, how can I prevent it from calculating if the variable it depends on is undefined?
To see the error, type something in either of the fields, and then delete it, so it becomes empty.
<script>
let num = "";
let secondNum = "";
$: output = "prefix" + num.toString() + secondNum.toString() + "suffix";
function handleChange() {
console.log(num, secondNum);
}
function handleSubmit(e) {
e.preventDefault();
}
</script>
<form on:submit={handleSubmit}>
<input type="number" bind:value={num} on:change={handleChange}>
<input type="number" bind:value={secondNum} on:change={handleChange}>
<button type="submit">
Submit
</button>
</form>

Clearing a numeric input causes its bound value to be undefined. num.toString() is an error if num is undefined (that's a JavaScript thing, not a Svelte thing).
Easiest fix would be this:
$: output = `prefix${num || ''}${secondNum || ''}suffix`;

Related

How to conditonally apply attribute in angular?

I have this problem:
I want to compare variable to ngModel input.
I'm doing that with directive:
Html:
<input type='text' ng-model='firstPerson.name' same-as-person='secondPerson.name'>
JS:
app.directive('sameAsPerson'), function() {
return {
require: 'ngModel',
restrict: 'A',
link: function ($scope, $element, $attrs, ctrl) {
var validate = function (firstValue) {
var secondValue = $attrs.sameAsPerson;
ctrl.$setValidity('sameAsPerson', firstValue == secondValue);
return firstValue ;} ;
ctrl.$parsers.unshift(validate);
ctrl.$formatters.unshift(validate);
$attrs.$observe('sameAsPerson', function(secondValue) {
return validate (ctrl.$viewValue);})}} ;}) ;
SameAsPerson is a costume directive that requires ngModel, restrict 'A' and set validity on the input based on the comparison between the values.
It works fine - if the firstPerson.name not equals to secondPerson.name the input border is red.
But!
In case there is not secondPerson on the scope I don't want the attribute same-as-person to be rendered to the html.
I tried to use the ng-attr but it doesn't seem to work.
In the current scenario if secondPerson doesn't exist the value of secondPerson.name in the directive is empty string.
Notice that in case secondPerson exist but the name is "" I still want to show red input.
In addition to that I compare many attributes of those two persons, not just the name, this is why I want to it be with directive and not with ngIf, ngStyle is also not the solution for me because there is more changes than just on the input itself.
Thank you very much for you help!
Only for style you can use ng-class directive.
<input ng-model="'firstPerson.name" ng-class="{ 'error':'secondPerson.name!='firstPerson.name' && secondPersonNameExist()"></input>
$scope.secondPersonNameExist = function () {
return angular.isDefined($scope.secondPerson.name);
}
Check this fiddle
Note that the class that you see is the previous so when the validation is clean you see error and on the next change you see the error absent. This is due to ng-change function is not picking up the new class status of input.

Manipulating displayed value and committedValue on core-input

I need to manipulate values from a raw API data for display to the user and manipulate them again before sending the update through the API. I'm using core-input for each value, but I'm having difficulty setting the initial value and binding to the correct update event.
<input id="host" is="core-input">
My first problem is that I don't know how to set and manipulate the initial value without also binding to the live changes stream. I tried binding only to committedValue but it does not set the initial value for the field.
However, even when I set commitedValue, I am unable to trigger it. I enter text into the field and then switch fields or press the enter key and nothing happens.
<input id="host" commitedValue="{{record | setHost}}" is="core-input">
And the JavaScript:
setHost: {
toDOM: function(record) {
if(record.host === "#"){
return record.domain;
} else {
return record.host + "." + record.domain;
}
},
toModel: function(value) {
if(record.host === "#"){
return record.domain;
} else {
return record.host + "." + record.domain;
}
}
}
To set the initial value, I think you can do a one-time binding.
<template is="auto-binding">
<input is="core-input" type="text" value="[[foo]]">
</template>
<script>
var tmpl = document.querySelector('template');
tmpl.foo = 'bar';
</script>
It seems like the approach you're trying to take with commitedValue may not be supported, because you can't actually write to commitedValue.
From the core-input docs on commitedValue
Setting this property has no effect on the input value.
It might be better to listen to on-change or on-blur (or both), handle the change, and then manually update value

Is there a way to capture the id of the dom element in a variable?

I have an element in "this" how do i get its id's value (and class's value)?
alert(this.id) ;
returns undefined.
First of all you should check if this is really your target element and not global window object. Let me illustrate my advice:
function foo() {
if (this === window) {
alert("'this' is actually 'window'");
} else {
alert("'this' is not 'window'");
}
}
foo(); // will alert: 'this' is actually 'window'
but:
document.onclick = foo;
// every mouse click will produce alert: 'this' is not 'window'
Anyway, I'd suggest you to use Firebug/Chrome console to inspect the real value of this object:
console.log(this); // will reveal you the real nature of _this_ ;-)
Probable duplicate for this.
You need to send the ID as the function parameters. Do it like this:
<button id="1" onClick="reply_click(this.id)">B1</button>
<button id="2" onClick="reply_click(this.id)">B2</button>
<button id="3" onClick="reply_click(this.id)">B3</button>
<script type="text/javascript">
function reply_click(clicked_id)
{
alert(clicked_id);
}
</script>
This will send the ID this.id as clicked_id which you can use in your function. See it in action here.

form segmentation value 'each' loop ajax request

I have a html form to get information from users. I segment this information to launch from each segment an ajax request (the segmentation is done following ">" characters). However, when I did not use 'each' jquery function (so without segmentation) ajax works, but with each jquery function ajax does not work at all and the loop does not work.
This is my javascript:
$(document).ready(function() {
$('#formu').on('submit', function() {
var sequence = $('#sequence').val().split(">"); // I segment here
$.each(sequence, function(k){ // for each segment I launch a request with the segment as argument
if (sequence[k].length != 0){
alert(sequence[k]);
$.ajax({
url:'run.py',
type:$(this).attr('method'),
data: {'sequence':">"+sequence[k]}, // the segment is given to python script
success: function(data){
$('#result').html(data);
}
});
} // enf if
//return false;
}); // end of each
}); // end of submit
}); // end of jquery
This is my html:
MyPage
<form method="post" id="formu" >
<textarea id="sequence" name="sequence" cols="80" rows="10"></textarea>
<br/>
<input type="submit" value="Submit">
</form>
<div id="result">
</div>
example of input:
>mysequence 1
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
>mysequence 2
BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
>mysequence 3
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
When you loop through an array using jQuery.each. You get passed key, value pairs into the function. What you were doing was getting the value back from the key, while it is already passed. There is no need to do that. Also, instead of returning false you can also prevent the event from doing its default behaviour
$('#formu').on('submit', function(e) {
e.preventDefault(); // Prevent default behavior
var sequence = $('#sequence').val();
alert(sequence); // Check this value
sequence = sequence.split(">");
$.each(sequence, function(key, value){
alert(value); // Alert is better placed here so you know what 'value' is
if (value.length != 0){
$.ajax({
url : 'run.py',
type : $("#formo").attr('method'), // Replaced 'this' with your form as 'this' might mean something you are not expecting here
data : { 'sequence' : ">"+value },
success : function(data){
$('#result').html(data);
}
});
}
});
});
As we don't know about you getting errors it is hard to do more than 'general improvements' to your code.
I think the reason it does not work might be because you use this in a $.each loop which might refer to the string instead of the form.

AngularJS - Server side validation and client side forms

I am trying to understand how to do the following things:
What is the accepted way of declaring a form. My understanding is you just declare the form in HTML, and add ng-model directives like so:
ng-model="item.name"
What to send to the server. I can just send the item object to the server as JSON, and interpret it. Then I can perform validation on object. If it fails, I throw a JSON error, and send back what exactly? Is there an accepted way of doing this? How do I push validation errors from the server to the client in a nice way?
I really need an example, but Angulars docs are pretty difficult to understand.
Edit: It seems I've phrased my question poorly.
I know how to validate client side, and how to handle error/success as promise callbacks. What I want to know, is the accepted way of bundling SERVER side error messages to the client. Say I have a username and password signup form. I don't want to poll the server for usernames and then use Angular to determine a duplicate exists. I want to send the username to the server, validate no other account exists with the same name, and then submit form. If an error occurs, how do I send it back?
What about pushing the data to the server as is (keys and values) with an error field appended like so:
{
...data...
"errors": [
{
"context": null,
"message": "A detailed error message.",
"exceptionName": null
}
]
}
Then binding to the DOM.
I've also been playing around with this kind of thing recently and I've knocked up this demo. I think it does what you need.
Setup your form as per normal with any particular client side validations you want to use:
<div ng-controller="MyCtrl">
<form name="myForm" onsubmit="return false;">
<div>
<input type="text" placeholder="First name" name="firstName" ng-model="firstName" required="true" />
<span ng-show="myForm.firstName.$dirty && myForm.firstName.$error.required">You must enter a value here</span>
<span ng-show="myForm.firstName.$error.serverMessage">{{myForm.firstName.$error.serverMessage}}</span>
</div>
<div>
<input type="text" placeholder="Last name" name="lastName" ng-model="lastName"/>
<span ng-show="myForm.lastName.$error.serverMessage">{{myForm.lastName.$error.serverMessage}}</span>
</div>
<button ng-click="submit()">Submit</button>
</form>
</div>
Note also I have added a serverMessage for each field:
<span ng-show="myForm.firstName.$error.serverMessage">{{myForm.firstName.$error.serverMessage}}</span>
This is a customisable message that comes back from the server and it works the same way as any other error message (as far as I can tell).
Here is the controller:
function MyCtrl($scope, $parse) {
var pretendThisIsOnTheServerAndCalledViaAjax = function(){
var fieldState = {firstName: 'VALID', lastName: 'VALID'};
var allowedNames = ['Bob', 'Jill', 'Murray', 'Sally'];
if (allowedNames.indexOf($scope.firstName) == -1) fieldState.firstName = 'Allowed values are: ' + allowedNames.join(',');
if ($scope.lastName == $scope.firstName) fieldState.lastName = 'Your last name must be different from your first name';
return fieldState;
};
$scope.submit = function(){
var serverResponse = pretendThisIsOnTheServerAndCalledViaAjax();
for (var fieldName in serverResponse) {
var message = serverResponse[fieldName];
var serverMessage = $parse('myForm.'+fieldName+'.$error.serverMessage');
if (message == 'VALID') {
$scope.myForm.$setValidity(fieldName, true, $scope.myForm);
serverMessage.assign($scope, undefined);
}
else {
$scope.myForm.$setValidity(fieldName, false, $scope.myForm);
serverMessage.assign($scope, serverResponse[fieldName]);
}
}
};
}
I am pretending to call the server in pretendThisIsOnTheServerAndCalledViaAjax you can replace it with an ajax call, the point is it just returns the validation state for each field. In this simple case I am using the value VALID to indicate that the field is valid, any other value is treated as an error message. You may want something more sophisticated!
Once you have the validation state from the server you just need to update the state in your form.
You can access the form from scope, in this case the form is called myForm so $scope.myForm gets you the form. (Source for the form controller is here if you want to read up on how it works).
You then want to tell the form whether the field is valid/invalid:
$scope.myForm.$setValidity(fieldName, true, $scope.myForm);
or
$scope.myForm.$setValidity(fieldName, false, $scope.myForm);
We also need to set the error message. First of all get the accessor for the field using $parse. Then assign the value from the server.
var serverMessage = $parse('myForm.'+fieldName+'.$error.serverMessage');
serverMessage.assign($scope, serverResponse[fieldName]);
I've got similar solution as Derek, described on codetunes blog. TL;DR:
display an error in similar way as in Derek's solution:
<span ng-show="myForm.fieldName.$error.server">{{errors.fieldName}}</span>
add directive which would clean up an error when user change the input:
<input type="text" name="fieldName" ng-model="model.fieldName" server-error />
angular.module('app').directive 'serverError', ->
{
restrict: 'A'
require: '?ngModel'
link: (scope, element, attrs, ctrl) ->
element.on 'change', ->
scope.$apply ->
ctrl.$setValidity('server', true)
}
Handle an error by passing the error message to the scope and telling that form has an error:
errorCallback = (result) ->
# server will return something like:
# { errors: { name: ["Must be unique"] } }
angular.forEach result.data.errors, (errors, field) ->
# tell the form that field is invalid
$scope.form[field].$setValidity('server', false)
# keep the error messages from the server
$scope.errors[field] = errors.join(', ')
Hope it would be useful :)
Well, the Answer Derek Ekins gave is very nice to work on. But: If you disable the submit button with ng-disabled="myForm.$invalid" - the button will not automatically go back to enabled as the server-based error state doesn't seem to be changed. Not even if you edit ALL fields in a form again to comply with valid inputs (based on client side validation).
By default, the form is submitted normally. If you don't provide a name property for each field in the form then it won't submit the correct data. What you can do is capture the form before it submitted and submit that data yourself via ajax.
<form ng-submit="onSubmit(); return false">
And then in your $scope.onSubmit() function:
$scope.onSubmit = function() {
var data = {
'name' : $scope.item.name
};
$http.post(url, data)
.success(function() {
})
.failure(function() {
});
};
You can also validate the data by setting up required attributes.
If you choose ngResource, it would look like this
var Item = $resource('/items/');
$scope.item = new Item();
$scope.submit = function(){
$scope.item.$save(
function(data) {
//Yahooooo :)
}, function(response) {
//oh noooo :(
//I'm not sure, but your custom json Response should be stick in response.data, just inspect the response object
}
);
};
The most important thing is, that your HTTP-Response code have to be a 4xx to enter the failure callback.
As of July 2014, AngularJS 1.3 has added new form validation features. This includes ngMessages and asyncValidators so you can now fire server side validation per field prior to submitting the form.
Angular 1.3 Form validation tutorial :
Taming forms in Angular 1.3
Video | Repo | Demo
References:
ngMessages directive
ngModel.NgModelController
I needed this in a few projects so I created a directive. Finally took a moment to put it up on GitHub for anyone who wants a drop-in solution.
https://github.com/webadvanced/ng-remote-validate
Features:
Drop in solution for Ajax validation of any text or password input
Works with Angulars build in validation and cab be accessed at formName.inputName.$error.ngRemoteValidate
Throttles server requests (default 400ms) and can be set with ng-remote-throttle="550"
Allows HTTP method definition (default POST) with ng-remote-method="GET"
Example usage for a change password form that requires the user to enter their current password as well as the new password.:
Change password
Current
Required
Incorrect current password. Please enter your current account password.
<label for="newPassword">New</label>
<input type="password"
name="newPassword"
placeholder="New password"
ng-model="password.new"
required>
<label for="confirmPassword">Confirm</label>
<input ng-disabled=""
type="password"
name="confirmPassword"
placeholder="Confirm password"
ng-model="password.confirm"
ng-match="password.new"
required>
<span ng-show="changePasswordForm.confirmPassword.$error.match">
New and confirm do not match
</span>
<div>
<button type="submit"
ng-disabled="changePasswordForm.$invalid"
ng-click="changePassword(password.new, changePasswordForm);reset();">
Change password
</button>
</div>
As variant
// ES6 form controller class
class FormCtrl {
constructor($scope, SomeApiService) {
this.$scope = $scope;
this.someApiService = SomeApiService;
this.formData = {};
}
submit(form) {
if (form.$valid) {
this.someApiService
.save(this.formData)
.then(() => {
// handle success
// reset form
form.$setPristine();
form.$setUntouched();
// clear data
this.formData = {};
})
.catch((result) => {
// handle error
if (result.status === 400) {
this.handleServerValidationErrors(form, result.data && result.data.errors)
} else {// TODO: handle other errors}
})
}
}
handleServerValidationErrors(form, errors) {
// form field to model map
// add fields with input name different from name in model
// example: <input type="text" name="bCategory" ng-model="user.categoryId"/>
var map = {
categoryId: 'bCategory',
// other
};
if (errors && errors.length) {
// handle form fields errors separately
angular.forEach(errors, (error) => {
let formFieldName = map[error.field] || error.field;
let formField = form[formFieldName];
let formFieldWatcher;
if (formField) {
// tell the form that field is invalid
formField.$setValidity('server', false);
// waits for any changes on the input
// and when they happen it invalidates the server error.
formFieldWatcher = this.$scope.$watch(() => formField.$viewValue, (newValue, oldValue) => {
if (newValue === oldValue) {
return;
}
// clean up the server error
formField.$setValidity('server', true);
// clean up form field watcher
if (formFieldWatcher) {
formFieldWatcher();
formFieldWatcher = null;
}
});
}
});
} else {
// TODO: handle form validation
alert('Invalid form data');
}
}
As I understand the question is about passing errors from the server to the client. I'm not sure if there are well-established practices. So I'm going to describe a possible approach:
<form name="someForm" ng-submit="submit()" ng-controller="c1" novalidate>
<input name="someField" type="text" ng-model="data.someField" required>
<div ng-show="someForm.$submitted || someForm.someField.$touched">
<div ng-show="someForm.someField.$error.required" class="error">required</div>
<div ng-show="someForm.someField.$error.someError" class="error">some error</div>
</div>
<input type="submit">
</form>
Let's say a server returns an object of the following kind:
{errors: {
someField: ['someError'],
}}
Then you can pass the errors to the UI this way:
Object.keys(resp.errors).forEach(i => {
resp.errors[i].forEach(c => {
$scope.someForm[i].$setValidity(c, false);
$scope.someForm[i].$validators.someErrorResetter
= () => $scope.someForm[i].$setValidity(c, true);
});
});
I make each field invalid and add a validator (which is not really a validator). Since validators are called after every change, this let's us reset the error status.
You can experiment with it here. You might also want to check out ngMessages. And a couple of related articles.