I'm having some problems trying to use short circuiting on a web page I am making.
I am trying to use
document.webkitExitFullscreen() || document.mozCancelFullScreen() || document.exitFullScreen();
But it seems to stop on the first try, despite that I would have though it would continue after the first argument comes up as undefined.
If I simply type in
document.mozCancelFullScreen()
then it works fine
I was wondering if anyone could point me to what I'm doing wrong here
The screenshot is taken in firefox btw.
Thanks in advance
Your code is trying to call document.webkitExitFullscreen and if it returns a falsy value, call document.mozCancelFullScreen, etc.
But if document.webkitExitFullscreen itself is undefined you'll get an error trying to call it, and the code will stop running at that point.
Perhaps:
var exitFullScreen = document.webkitExitFullscreen || document.mozCancelFullScreen || document.exitFullScreen;
if (exitFullScreen) {
exitFullScreen.call(document); // Just `exitFullScreen();` may work as well
}
Or alternatively:
["webkitExitFullscreen", "mozCancelFullScreen", "exitFullScreen"].some(function(name) {
if (document[name]) {
document[name]();
return true;
}
});
...which avoids the whole "do I need call or not?" issue.
The problem is that you're already calling the function, so if it doesn't exist, you get an error.
You coudl try something like:
(document.webkitExitFullscreen || document.mozCancelFullScreen || document.exitFullScreen)();
Related
I've just come across a situation in which an if statement is constantly triggering despite the parameters not being true.
function draw(){
if(5<mouseX<10 && 5<mouseY<10){
background(100);
} else (background(200));
}
When running the above program, the background is always value 100, no matter where I move the mouse.
I've boiled this down from an attempt to make a button within a mouseClicked function in a successful attempt to find my fundamental problem of misunderstanding. I'm running it in p5js if that helps.
Your if-statement should be as follows:
if(5<mouseX && mouseX<10 && 5<mouseY && mouseY<10)
The reason behind this behaviour is:
if(5<mouseX<10 && 5<mouseY<10){
background(100);
} else (background(200));
When the javascript engine reads 5<mouseX it returns true then reads true<10 this is also true as here the js engine treats true as 1 and condition 1<10 is always true. This happens with other part of the expression also.
Try using :
if(5<mouseX && mouseX<10 && 5<mouseY && mouseY<10)
Ok, I've got an issue I don't understand.
I have a boolean value which I test and if true I do something.
BUT javascript never go in it even if the var is true.
I try this :
if(isConfigD)
handleConfigurationD;
this :
if(isConfigD == true)
handleConfigurationD;
And this :
if(isConfigD === true)
handleConfigurationD;
But nothing work whereas isConfigD is always set on true :(
What am I missing ?
You condition works well, but if you call a function, then you need parenthesis for the call.
handleConfigurationD();
// ^^
handleConfigurationD is just an identifier. That statement is going to have one of two outcomes:
A ReferenceError
"Yup, that's a bit of data"
Presumably you have stored a function in it and want to call the function.
handleConfigurationD();
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 doing an exercise on an online course to learn Javascript. This is only the first one and I am having issues, so I really want to understand it before I progress.
The question is this:
complete the while loop in the editor so it will print out "I'm learning while loops!". Do this by adding the condition between the parentheses—don't change line 5, or you could get an infinite loop!
The code is:
var understand = true;
while(){
console.log("I'm learning while loops!");
understand = false;
}
I tried adding this to the condition:
while(understand === 0){
But I am getting this error
Oops, try again. It looks like you didn't print the string to the console. Check your loop syntax!
What am I doing wrong in my condition? Could someone please elaborate, so I can learn the key fundamentals to this. Thanks!
The example before this exercise:
var coinFace = Math.floor(Math.random() * 2);
while(coinFace === 0){
console.log("Heads! Flipping again...");
var coinFace = Math.floor(Math.random() * 2);
}
console.log("Tails! Done flipping.");
Edit---update:
You may have noticed that when we give a variable the boolean value true, we check that variable directly—we don't bother with ===. For instance,
var bool = true;
while(bool){
//Do something
}
is the same thing as
var bool = true;
while(bool === true){
//Do something
}
but the first one is faster to type. Get in the habit of typing exactly as much as you need to, and no more!
If you happen to be using numbers, as we did earlier, you could even do:
It's while(understand === true)
Because the loop will fire the first time, as understand is already set to true. Then, as it's firing, it will set understand to false- so the next time it tries to fire the loop the condition will fail and it won't continue. This way, you're getting one execution of the loop- thus printing only one time.
If you had code that looks like this
while(true){
console.log("I'm learning while loops!");
understand = false;
}
you would get an infinite loop! The loop would just keep going because the conditional will always be true. Now if only there were some way, like a variable in the conditional, to make the conditional false.
Thanks for taking time to review this question. I've been trying to fix a problem for one or two hours with no success...
I have a web page that sets a JavaScript variable based on the response from a function:
grade = getScore(questionAnswer, userAnswer, questionType);
(userAnswer is the user's answer to a question and is retrieved from a textarea)
Here is getScore:
function getScore(questionAnswer, userAnswer, questionType) {
switch(questionType) {
case 'multiplechoice':
return scoreMC(questionAnswer, userAnswer);
break;
case 'usertypesanswer':
return scoreTA(questionAnswer, userAnswer);
break;
default:
return 0
}
}
The functions for scoreMC and scoreTA have been tested thoroughly and work great. The issue is that if a user's answer is not formatted correctly, scoreMC or scoreTA will return false. Otherwise it returns the values score and msg. However, instead of getting a "false" value for "grade" when I set the value of the grade variable based on the getScore function, I get "undefined". (We have no problems when the user response validates properly.)
After setting "grade", I have tried to check if any part of it is undefined:
if(typeof(grade.score) !== undefined)
I do not understand why, but even when I see "undefined" in my Firebug console, grade.score passes this check...
Does anyone see what I am doing wrong? Thank you very much for your assistance. I have a lot to learn about JavaScript.
if(typeof(grade.score) !== undefined)
can be
if(grade.score && grade.score !== false) // if I understand your question
or
if(typeof(grade.score) !== "undefined")
typeof returns a string
If no return statement is used (or an empty return with no value), JavaScript returns undefined.
It is almost certain that one of your score functions (scoreMC, scoreTA, whose code you should have included in the question) does not return a value i.e.
return;
Or just reaches the end of the function code block without encountering a return.