How can I exit the JavaScript script much like PHP's exit or die? I know it's not the best programming practice but I need to.
This question is related to
javascript
exit
die
If you use any undefined function in the script then script will stop due to "Uncaught ReferenceError". I have tried by following code and first two lines executed.
I think, this is the best way to stop the script. If there's any other way then please comment me. I also want to know another best and simple way. BTW, I didn't get exit or die inbuilt function in Javascript like PHP for terminate the script. If anyone know then please let me know.
alert('Hello');
document.write('Hello User!!!');
die(); //Uncaught ReferenceError: die is not defined
alert('bye');
document.write('Bye User!!!');
Simply create a BOOL condition , no need for complicated code here..
If even once you turn it to true/ or multiple times, it will both give you one line of solution/not multiple - basically simple as that.
If you are using Firefox or a Browser it cannot be done with most of these Console methods once you have started an iterator ( as you can see I have ). You can go to source and manually pause the execution of the script. ( This still does not Stop it completely per say)
There are many ways to exit a JS or Node script. Here are the most relevant:
// This will never exit!
setInterval((function() {
return;
}), 5000);
// This will exit after 5 seconds, with signal 1
setTimeout((function() {
return process.exit(1);
}), 5000);
// This will also exit after 5 seconds, and print its (killed) PID
setTimeout((function() {
return process.kill(process.pid);
}), 5000);
// This will also exit after 5 seconds and create a core dump.
setTimeout((function() {
return process.abort();
}), 5000);
If you're in the REPL (i.e. after running node on the command line), you can type .exit to exit.
In JavaScript multiple ways are there, below are some of them
Method 1:
throw new Error("Something went badly wrong!");
Method 2:
return;
Method 3:
return false;
Method 4:
new new
Method 5:
write your custom function use above method and call where you needed
Note: If you want to just pause the code execution you can use
debugger;
Not applicable in most circumstances, but I had lots of async scripts running in the browser and as a hack I do
window.reload();
to stop everything.
I know this is old, but if you want a similar PHP die() function, you could do:
function die(reason) {
throw new Error(reason);
}
Usage:
console.log("Hello");
die("Exiting script..."); // Kills script right here
console.log("World!");
The example above will only print "Hello".
This is an example, that, if a condition exist, then terminate the script. I use this in my SSE client side javascript, if the
<script src="sse-clint.js" host="https://sse.host" query='["q1,"q2"]' ></script>
canot be parsed right from JSON parse ...
if( ! SSE_HOST ) throw new Error(['[!] SSE.js: ERR_NOHOST - finished !']);
... anyway the general idea is:
if( error==true) throw new Error([ 'You have This error' , 'At this file', 'At this line' ]);
this will terminate/die your javasript script
Even in simple programs without handles, events and such, it is best to put code in a "main" function, even when it is the only procedure :
<script>
function main()
{
//code
}
main();
</script>
This way, when you want to stop the program you can use "return".
If you don't care that it's an error just write:
fail;
That will stop your main (global) code from proceeding. Useful for some aspects of debugging/testing.
i use return statement instead of throw as throw gives error in console. the best way to do it is to check the condition
if(condition){
return //whatever you want to return
}
this simply stops the execution of the program from that line, instead of giving any errors in the console.
"exit" functions usually quit the program or script along with an error message as paramete. For example die(...) in php
die("sorry my fault, didn't mean to but now I am in byte nirvana")
The equivalent in JS is to signal an error with the throw keyword like this:
throw new Error();
You can easily test this:
var m = 100;
throw '';
var x = 100;
x
>>>undefined
m
>>>100
I am using iobroker and easily managed to stop the script with
stopScript();
If you're looking for a way to forcibly terminate execution of all Javascript on a page, I'm not sure there is an officially sanctioned way to do that - it seems like the kind of thing that might be a security risk (although to be honest, I can't think of how it would be off the top of my head). Normally in Javascript when you want your code to stop running, you just return from whatever function is executing. (The return statement is optional if it's the last thing in the function and the function shouldn't return a value) If there's some reason returning isn't good enough for you, you should probably edit more detail into the question as to why you think you need it and perhaps someone can offer an alternate solution.
Note that in practice, most browsers' Javascript interpreters will simply stop running the current script if they encounter an error. So you can do something like accessing an attribute of an unset variable:
function exit() {
p.blah();
}
and it will probably abort the script. But you shouldn't count on that because it's not at all standard, and it really seems like a terrible practice.
EDIT: OK, maybe this wasn't such a good answer in light of Ólafur's. Although the die() function he linked to basically implements my second paragraph, i.e. it just throws an error.
This little function comes pretty close to mimicking PHP's exit(). As with the other solutions, don't add anything else.
function exit(Msg)
{
Msg=Msg?'*** '+Msg:'';
if (Msg) alert(Msg);
throw new Error();
} // exit
If you just want to stop further code from executing without "throwing" any error, you can temporarily override window.onerror as shown in cross-exit:
function exit(code) {
const prevOnError = window.onerror
window.onerror = () => {
window.onerror = prevOnError
return true
}
throw new Error(`Script termination with code ${code || 0}.`)
}
console.log("This message is logged.");
exit();
console.log("This message isn't logged.");
This code will stop execution of all JavaScripts in current window:
for(;;);In my case I used the window.stop API which is like clicking the X button on your browser:
window.stop();
Is a misuse of the concept but probably the only option. And, yes, you will have to reset all event listeners, just like the accepted answer mentions. You would also need a single point of entry if I am right.
On the top of it: You want a page which reports to you by email as soon as it throws - you can use for example Raven/Sentry for this. But that means, you produce yourself false positives. In such case, you also need to update the default handler to filter such events out or set such events on ignore on Sentry's dashboard.
This does not work during the loading of the page. It stops decoding of the page as well. So you cannot really use it to offer user a javascript-free variant of your page.
Stops execution only with debugger opened. Works great, but not a deliverable.
Place the debugger; keyword in your JavaScript code where you want to stop the execution. Then open your favorite browser's developer tools and reload the page. Now it should pause automatically. Open the Sources section of your tools: the debugger; keyword is highlighted and you have the option to resume script execution.
I hope it helps.
More information at:
i use this piece of code to stop execution:
throw new FatalError("!! Stop JS !!");
you will get a console error though but it works good for me.
I think this question has been answered, click here for more information. Below is the short answer it is posted.
throw new Error("Stop script");
You can also used your browser to add break points, every browser is similar, check info below for your browser.
For Chrome break points info click here
For Firefox break points info click here
For Explorer break points info click
For Safari break points info click here
Source: Stackoverflow.com