I'm very new to JS - only a couple days in.
Trying to write a very basic prompt evaluated by an if statement.
When I run the code below, the user is prompted, but the statement is never evaluated by the if statement.
Any help? -- I realize the answer is probably simple and obvious, but as a SUPER beginner, what do I do?
var bool = prompt("What is an example of a boolean?");
if (typeof(bool) === "boolean") {
print("correct! that is a boolean");
print(bool) ;
};
In this case, assuming the user inputs something in the prompt, the type of the bool variable will always be a string. You'd rather check if the input compares to the string "true" or "false" etc., like this:
if (bool.toLowerCase() == "true" || bool.toLowerCase() == "false") {
...
}
Related
I'm trying to disable a form in a JSP just when two conditions become true. I've tried a var variable set false so when my if-else condition becomes true it becomes true. But it is not working.
Here is my code. (not sure if it can help but I'm using eclipse)
var disabled=false;
then I've created the function
function isDisable(){
if($("#idCost").val() == 1 && $("#IdBasket").val() == "3"){
disabled=true;
}
}
and then set in the form field
< disabled="false"/>
What am I doing wrong?
Thanks for helping
It looks like your code is in JavaScript and not Java, even though you say you are writing a JSP.
Your JS code compare one return to a Number (val() == 1) and another to a String val() == "3". Did you try making them both the same? If .val() is returning strings, then they should both compare to strings. If .val() is returning numbers, then they should both compare to numbers.
I am developing a webpage with fairly simple JavaScript. My entire JavaScript code is:
function showUnlockPopup(isViolated,instId,unlock_done,unlock_total,period,endDate){
alert(isViolated);
if(isViolated){
if(unlock_done < unlock_total){
showInfoPopup(instId,unlock_done,unlock_total,period);
} else {
showNoUnlocksPopup(instId,unlock_done,unlock_total,period,endDate);
}
} else {
showNotViolatedModal();
}
}
However, irrespective of the value of the 'isViolated' variable, my 'showInfoPopup' function is called.
I have checked the code for the method call too:
<button onClick="showUnlockPopup(isViolated)">Unlock</button>
The alert shows 'true' or 'false' values correctly, but the logic runs for only 'true' irrespective of the value.
I think I am missing something fairly basic here. I tried a lot, but of no use. Kindly help me with the same.
it is because isViolated is returned as a string. so unless the string is null it will be true if it has some contents. You should change your check to isViolated == 'true', make a new variable that is a boolean and assign it depending on isViolated or something third.
I am working on a question for a course for learning javascript. I am running into trouble trying to add an if statement inside of a switch. I currently have:
var user = prompt("Are you ready for battle?!").toUpperCase();
switch(user) {
case'YES':
if(YES && NO) {
console.log("Great, let's do it.");
} else {
console.log("Bye");
}
console.log("Great! It will be a long exciting battle.");
break;
case'NO':
console.log("Come back when you are ready.");
break;
case'MAYBE':
console.log("Go away. This is only for the brave");
break;
default:
console.log("You obviously do not belong here. It was a simple yes/no question.")
}
The question is this:
Add some if/else statements to your cases that check to see whether one
condition and another condition are true, as well as whether one condition
or another condition are true. Use && and || at least one time each.
The error I am getting is this: ReferenceError: YES is not defined
What can I put in the if's condition to make this work or how do I define YES?
It would appear that you have two problems working against you here.
First is the issue pointed out in comments that you're treating YES and NO like variables, and they aren't. To avoid robbing you of the opportunity to learn by providing a corrected version of your code, I'll only give relevant examples.
var word = "test";
// If we compare against the string literally, it will have an error
// because it's looking for a variable with that name.
if (word === test) { } // ReferenceError: test is not defined
// we fix this by quoting what we're comparing against
if (word === "test") { } // Code inside the block would be executed :)
// But what about checking the value of "test" by itself?
// A string is "truthy", meaning that it passes the conditional test always.
if ("test") { } // Code would be executed always regardless of the content of var word
// Stringing multiple constants together doesn't make sense
if ("test" && "word") { } // This is equivalent...
if (true && true) { } // ... to this, which doesn't make sense
This brings us to the second problem you're trying to solve. The requirements for your problem specify checking if one condition AND another are true, as well as one condition OR another. The problem is that you only have one conditional to check: the status of the variable user.
It only makes sense to test the condition of something if you don't know what it is. Input received from a user is a perfect example. So I'd recommend that you take more inputs from the user such as name, age, gender, shoe size, or anything else. You can then check conditions as follows:
// You would need to store user input in variables username and age previously...
if (username === "vastlysuperiorman" && age < 13) { console.log("You're awfully young!"); }
// Or to only allow people within an age range...
if (age < 13 || age > 31) { console.log("You must be between 13 and 31 years old to play this game!"); }
Once you have multiple conditions to check, you can check them anywhere--inside a function, inside a case statement, inside another if. It doesn't matter. Just add an if block and test the conditions. :)
Ok so I've been stumped on this one for days and its frustrating me. (Will frustrate me even more if it's something simple I'm overlooking).
I have a form generated in PHP which I want to verify that certain pieces are filled out. I do this via a JavaScript check when the user clicks the submit button.The JavaScript code is below:
<script language="JavaScript">
function checkFields()
{
if (document.getElementById('ldescription').value == '' || document.getElementById('uname').value == ''
|| document.getElementById('sdescription').value == '' || document.getElementById('email').value == ''
|| document.getElementById('platf').value == "Select Group" || document.getElementByID('cate').value == "Select Category" )
{
alert("Please fill out all of the starred (*) items" );
return false;
}
}
</script>
For some reason though this only checks the ldescription field. If that field has text but all the others are empty it carries on like everything was filled out. Also if I change the order of my checks and ldescription is anywhere but the first check, it will do no check whatsoever even when all the fields are empty.
Any ideas?
EDIT:
Got it fixed. Along with the suggestion I marked as correct the document.getElementById('item').value command worked with only textarea boxes but not regular text input boxes. By changing the command to document.MyForm.myTextName.value everything fell into place.
Couple of problems i noticed with your sample code.
The last getElementById call has improper casing. The final d is capitalized and it shouldn't be
Comparing the value to a string literal should be done by === not ==.
JSLint complains there are line break issues in your if statement by having the line begin with || instead of having the previous line end with ||.
The first and third items are most likely the ones causing your problem.
Inside your if condition, when you are breaking a line, make sure that the last token in the line is the OR operator ||.
Javascript does semicolon insertion, so it may be that semicolons are being inserted (automatically, invisibly, by the interpreter) in a bad place.
Try the below code
<script language="JavaScript">
function checkFields()
{
if (document.getElementById('ldescription').value === '' ||
document.getElementById('uname').value === '' ||
document.getElementById('sdescription').value === '' ||
document.getElementById('email').value === '' ||
document.getElementById('platf').value === "Select Group" ||
document.getElementById('cate').value === "Select Category")
{
alert("Please fill out all of the starred (*) items" );
return false;
}
}
</script>
Please use Javascript && operator which returns true if both the elements are true. || operator evaluates to true in case atleast one of the element is true which is what is happening in your case. You can take a look at Javascript boolean Logic
I've got the following jQuery (I've got it wrapped in the document ready function and all that, so please know I'm just showing you the inside of the function.
..
var itemIsSold = $("#itemIsSold").val();
alert(itemIsSold);
if(!itemIsSold) {
...
}
where itemIsSold is a hidden input field. I get the value False upper case F when it hits the alert but never enters my next if statement. I know this has to be something stupid simple.
If the input's value contains the string "False", that will not translate into a false boolean value. You will need to actually check for itemIsSold == "False".
Since the value of the hidden input field is a string, !"False" will be evaluated to false. Note that any string other than a string with the length of 0 is treated as true. So you should rather compare the string value to another string value like "False":
if (itemIsSold == "False") {
// …
}