AddPatient = {};
AddPatient.Firstname = FirstNameValue || PatientModel.errorMsg('FirstName',FirstNameValue);
AddPatient.LastName = LastNameValue || PatientModel.errorMsg('LastName',LastNameValue);
AddPatient is an Object and i am checking it whether its blank or not before sending the request.
PatientModel.js
errorMsg: function(title,FirstNameValue,LastNameValue) {
if(FirstNameValue === undefined || FirstNameValue === ' ' && LastNameValue === undefined || LastNameValue = ' ') {
alert('FirstName and LastName are missing');
return false;
} else {
alert(+title 'is missing');
return false;
}
}
I have a form, where i have FirstName and LastName field and i have to check it should not be blank. I want a single function in javascript which can work.
Is this the right way to do it?
I can see a couple of problems in your code.
Mismatch between errorMsg()'s expected arguments and how it is called
Syntax error in second alert()
Bad expression inside if statement
Mismatch between errorMsg()'s expected arguments and how it is called
Your errorMsg() function expects three arguments, but you only pass it two at a time:
errorMsg: function(title,FirstNameValue,LastNameValue) {
....
}
... and then ....
.errorMsg('FirstName',FirstNameValue);
.errorMsg('FirstName',LastNameValue);
If you really want to use both values inside errorMsg(), you need to pass them both every time, in the same order the function expects them:
PatientModel.errorMsg('FirstName',FirstNameValue,LastNameValue);
PatientModel.errorMsg('LastName',FirstNameValue,LastNameValue);
// This is weird code, but it'll work
Syntax error in second alert()
This is simple enough to fix, and could have been just a typo.
alert(+title 'is missing');
^ ^_There's something missing here.
|_This will only try to convert title to a number
What you want is this:
alert(title + 'is missing');
Bad expression inside if statement
if(FirstNameValue === undefined || FirstNameValue === ' ' && LastNameValue === undefined || LastNameValue = ' ') {
This won't work as you expect, because && has greater precedence than ||, meaning the expression will be evaluated as such:
if (
FirstNameValue === undefined
|| (FirstNameValue === ' ' && LastNameValue === undefined)
|| LastNameValue = ' '
) {
You would need parenthesis to fix the precedence:
if( (FirstNameValue === undefined || FirstNameValue === ' ') && (LastNameValue === undefined || LastNameValue = ' ') ) {
This is irrelevant, actually, because the expression can be simplified like this:
// If these values are taken from a form input, they are guaranteed to be strings.
if(FirstNameValue.length === 0 && LastNameValue.length === 0) {
Or even better, like this:
// Uses regular expressions to checks if string is not whitespace only
var WHITESPACE = /^\s*$/;
if( WHITESPACE.test(FirstNameValue) && WHITESPACE.test(FirstNameValue)){
How I would fix your code
This would be an incomplete answer if I didn't provide a correct version of your code, so here it goes. Notice that I separate filling-in of information and its validation in two steps.
PatientModel.js :
validate: function(patient){
var WHITESPACE = /^\s*$/;
var errors = [];
if( WHITESPACE.test(patient.FirstName) ){
// No first name
if( WHITESPACE.test(patient.LastName) ){
// No last name either
errors.push('FirstName and LastName are missing');
}
else {
// Only first name missing
errors.push('FirstName is missing');
}
}
else if( WHITESPACE.test( patient.LastName) ){
// Only last name missing
errors.push('LastName is missing');
}
// Returns array of errors
return errors;
}
Your other code:
AddPatient = {};
AddPatient.Firstname = FirstNameValue;
AddPatient.LastName = LastNameValue;
errors = PatientModel.validate(AddPatient);
if( errors.length != 0 ){
alert('You have the following errors:\n' + errors.join('\n'));
}
Edit: a different, perhaps better, approach. The only difference is we now write validate() as a method of a Patient object:
>>> PatientModel.js:
var WHITESPACE = /^\s*$/;
// Creates a new empty Patient
function Patient(){
this.FirstName = '';
this.LastName = '';
}
// Adds a validate() method to all Patient instances
Patient.prototype.validate: function(){
var errors = [];
if( WHITESPACE.test(this.FirstName) ){
// No first name
if( WHITESPACE.test(this.LastName) ){
// No last name either
errors.push('FirstName and LastName are missing');
}
else {
// Only first name missing
errors.push('FirstName is missing');
}
}
else if( WHITESPACE.test( thisLastName) ){
// Only last name missing
errors.push('LastName is missing');
}
// Returns array of errors
return errors;
}
>>> Your other code :
patient = new Patient();
patient.FirstName = FirstNameValue;
patient.LastName = LastNameValue;
errors = patient.validate();
if( errors.length != 0 ){
alert('You have the following errors:\n' + errors.join('\n'));
}
I would recommend using the Jquery validate plugin for this functionality. It will let you do a hole range of clientside validation. Including required validation.
If you just want pure javascript then your method is fine. I'd make it a more generic validate method which would check each validation rule you have and if it fails add the message to an array. After all your checks are finished if the count of the array is grater then zero then output complete list of errors.
Related
I am doing a mini-API on Express.
On an request, I want to verify that all the query parameters are filled.
Hence, my intuition led me to this:
app.get("/book", (req, res) => {
console.log(req.query.seats, req.query.category, req.query.date);
let isEmpty =
req.query.seats === undefined ||
req.query.category === undefined ||
req.query.date === undefined;
console.log(isEmpty);
if (isEmpty === true) {
console.log("here3");
res.status(400).send("Missing input");
}
// else continue with instructions
}
Nevertheless, the console outputs false for isEmpty, while it tells that elements (req.query.category) is undefined, passing to the next instruction and not catching the error.
Does the elements have a different behavior in a console log and and comparison ?
thanks !
If you want to check for undefined AND empty string without problem you could do this way :
let isEmpty = !req.query.seats || !req.query.category || !req.query.date
For example :
var seats = '';
var category = undefined;
var date = '';
let isEmpty = !seats || !category || !date
console.log(isEmpty) // true
Let's say I have this if statement:
if (
username === firstname &&
password !== fakePassword &&
givenname === lastname
) {
console.log(`Hi ${firstname}`)
}
Now I want to make the given name required if it's longer than 3 characters:
const givennameRequired = givenname.length > 3;
can I alter the if statement in a way that says "If the givennameRequired variable is true then worry about this part"
This way the console logs against two params or three depending on the validity of givennameRequired. Obviously I'm trying to avoid using an if/else and having two console logs
In a rough "sudo-code" way (I know this isn't valid):
if (
username === firstname &&
password !== fakePassword &&
(
if (givennameRequired) {
givenname === lastname
} else {
return true;
}
)
) {
console.log(`Hi ${firstname}`)
}
Basically, if the length is greater than three evaluate givenname === lastname otherwise, return true and don't worry about it.
This may do what you want:
if (
username === firstname &&
password !== fakePassword &&
(givenname.length <= 3 || givenname === lastname)
) {
console.log(`Hi ${firstname}`)
}
The if condition only bothers to check givenname === lastname if givenname.length > 3
This can be easily achieved with an if statement
if (givenname.length > 3){
//do something
}
else {
//do something else
}
Trying to keep in line with your syntax. Something like this should work. For your own sanity I'd consider nesting the if statements so you can provide more accurate feedback to the user.
if (username === firstname && password !== fakePassword && (givennamerequired == true && givenname === lastname && givenname.length() > 3))
) {
console.log(`Hi ${firstname}`)
}
I'm populating a table with data - using fixed-data-table, which is a React.js component. However, that isn't so important at this stage.
The table has a search box where the issue stems from.
First, here's the interesting part of the code.
for (var index = 0; index < size; index++) {
if (!filterBy || filterBy == undefined) {
filteredIndexes.push(index);
}
else {
var backendInfo = this._dataList[index];
var userListMap = hostInfo.userList;
var userListArr = Object.values(userListMap);
function checkUsers(){
for (var key in userListArr) {
if (userListArr.hasOwnProperty(key) && userListArr[key].text.toLowerCase().indexOf(filterBy) !== -1) {
return true;
}
}
return false;
}
if (backendInfo.firstName.indexOf(filterBy) !== -1 || backendInfo.lastName.toLowerCase().indexOf(filterBy) !== -1 || backendInfo.countryOrigin.toLowerCase().indexOf(filterBy) !== -1
|| backendInfo.userListMap.indexOf(filterBy) !== -1) {
filteredIndexes.push(index);
}
}
}
This is rendered and the last part is throwing errors if you input something in the table, and a column returns null from the user input.
The thing is, I can make the code work if I change the last part to ..
try {
if (backendInfo.firstName.indexOf(filterBy) !== -1 || backendInfo.lastName.toLowerCase().indexOf(filterBy) !== -1 || backendInfo.countryOrigin.toLowerCase().indexOf(filterBy) !== -1
|| backendInfo.userListMap.indexOf(filterBy) !== -1) {
filteredIndexes.push(index);
}
}
catch(err) {
console.log('Exception')
}
With the try/catch, it works 100% as intended and handles the indexOf returning null... But this can't be the way to properly handle it - I'm assuming this sort of exception handling is, well, supposed to be for rare exceptions, and shouldn't really be used on the front-end as much as the backend.
How do I handle indexOf returning null in the above Javascript code? It might return null in any of the sources columns that are being populated.
If a key cannot be found, JS will throw an error. Try-catch is a good way to fix these errors, but there is an alternative:
You could check if keys exist in an object prior to pushing a value into it.
var data = { };
var key = "test";
// your method works great
try {
var value = data.firstname.indexOf(key);
} catch (err) {}
// another method, I'd prefer the try/catch
var value = data.firstname ? data.firstname.indexOf(key) : undefined;
// test if the object is the type of object you are looking for
// this is in my opinion the best option.
if(data.firstname instanceof Array){
var value = data.firstname.indexOf(key);
}
// you can use the last option in your code like this:
var firstnameHasKey = data.firstname instanceof Array && ~data.firstname.indexOf(key);
var lastnameHasKey = data.lastname instanceof Array && ~data.lastname.indexOf(key);
if(firstnameHasKey || lastnameHasKey){
// logics
}
If you test the instanceof && indexOf, there will never be an error. If firstname is undefined, the indexOf will never be checked.
Ofcourse you can use this for other types:
var myDate = new Date();
myDate instanceof Date; // returns true
myDate instanceof Object; // returns true
myDate instanceof String; // returns false
MDN documentation
How to check with if condition if response has a string , if response has a string then execute the if condition.basically if there is error from server i want to make $scope.ActiveFile true.
main.js
$scope.onError = function(e) {
console.log('Error while uploading attachment', e.XMLHttpRequest.response);
$scope.errorMessage = JSON.parse(e.XMLHttpRequest.response).techErrorMsg;
if ($scope.errorMessage >= 1){
$scope.applyActiveFile = true;
}
};
response.json
Server response: {"errorCode":500,"errorMsg":"Service failed. Please contact administrator.","techErrorMsg":"Sheet : PROCESS_INVENTORY not found in the File"}
To solve your specific query this should work
if ($scope.errorMessage != null/blank) //whatever suits you
{
$scope.applyActiveFile = true;
}
Now answering what your question heading says - to check if property is string
if (typeof response === string)
/*typeof tells the type of operator, it will return number in case of number and string in case of string*/
{
$scope.applyActiveFile = true;
}
As mic4ael said, you could use some condition such as:
if ($scope.errorMessage)
$scope.applyActiveFile = true;
You could use some regular expression such as:
if ((/^\s*$/).test($scope.errorMessage))
$scope.applyActiveFile = false;
...which would check if the string is empty or has only white spaces and turn your trigger to false. You'd only want to check one or two values with this, though cause it'll be performance-heavy otherwise.
Many other solutions...
Something like this
for (var i in $scope.errorMessages){
if (typeof $scope.errorMessages[i] === "string"){
alert($scope.errorMessages[i]);
}
}
To test in browser console input:
var a = {"errorCode":500,"errorMsg":"Service failed. Please contact administrator.","techErrorMsg":"Sheet : PROCESS_INVENTORY not found in the File","thirdFieldNotString":1};
for (var i in a){
if (typeof a[i] === "string"){
alert('Value is string');
}
};
I am running this line:
var good = data["good"] || false;
where data comes from the success method in a jquery ajax request.
But, what I thought that this would do is default good to false if data["good"] is null, but it is not.
Chrome is throwing this:
Uncaught TypeError: Cannot read property 'good' of null
and since it is null, shouldn't good then be set to false?
The problem is not that data["good"] is null, but that data itself is null.
Your code as is would be fine if data always has a value, but may not have property good. But unfortunately the JavaScript engine doesn't check if everything in a statement is undefined or null, i.e. it won't test data, and then test data["good"] and so on.
You need to test if data has at least some sort of value first, that is, it is "truthy".
Fix 1
You can lay it out clearly like so:
var good = false;
if(data && data["good"]) {
good = data["good"];
}
Fix 2
Or a neat shortcut is to use the fact that && and || will return the first "truthy" value found - it does not have to be a boolean:
var good = (data && data["good"]) || false;
The jquery tutorial on Operators has a good explanation of what is returned from the && and || operators.
// has a value - sets to "foo"
var data1 = { good: 'foo' };
var good1 = (data1 && data1["good"]) || false;
document.write("<div>" + good1 + "</div>");
// data is null - sets to false
var data2 = null;
var good2 = (data2 && data2["good"]) || false;
document.write("<div>" + good2 + "</div>");
// data["good"] doesn't exist - sets to false
var data3 = { bad: 'hello' };
var good3 = (data3 && data3["good"]) || false;
document.write("<div>" + good3 + "</div>");
Falsy Gotchas!
The other thing to be careful of is that some values you would want to store in your variable may evaluate to false, so you might incorrectly end up with good = false. This depends on what you expect to be inside data["good"].
This will occur for the following, again from the jquery site:
false - boolean false value
"" - Empty strings
NaN - "not-a-number"
null - null values
undefined - undefined values (i.e. if data doesn't have property "good")
0 - the number zero.
If you think this could be the case, you may need to be more specific in your checks:
var data = { good: 0 };
// 0 is falsy, so incorrectly sets to false
var good = (data && data["good"]) || false;
document.write("<div>" + good + "</div>");
// check the actual type and value - correctly set to 0
var good2 = (data && (typeof data["good"] != "undefined") && data["good"] != null)
? data["good"] : false;
document.write("<div>" + good2 + "</div>");
In your case, I can't imagine one-liner, which will check if data is not null and if so, put data[good] into variable.
You must first of all, get rid of Exception.
I would rather do:
var good = false;
if(data){
good = data["good"] || false;
}