if(a.value==1 && b.value==2)
{
try{callFunc() }catch(e) {}
}
frm.submit();
Inside function callFunc(), what do I have to write so that execution completely stops?
It should not execute frm.submit();
function callFunc()
{
//stop execution here -- ensure it won't execute fm.submit()
}
Better one is
function Abort()
{
throw new Error('This is not an error. This is just to abort javascript');
}
than from any where call this
try
{
for(var i=0;i<10;i++)
{
if(i==5)Abort();
}
} catch(e){}
For you
function callFunc()
{
//stop execution here
Abort();
}
//code from where you are going to call
try
{
if(a.value==1 && b.value==2)
{
callFunc()
}
frm.submit();
}
catch(e) {}
As you've discovered, aborting JavaScript almost always involves exceptions. If you truly can't change the wrapper, then you might have to resort to something a bit more extreme. One (evil) way to kill the script is to convince the browser that it's taking too long, by running an infinite loop:
function callFunc()
{
//stop execution here
var n = 1;
while (n) {
n += 1;
}
}
Modern browsers will let the user kill the script after a while. Granted, it will make your site seem broken, but that should give you the leverage you need to get a better API in place.
If the busy-loop is too extreme, you could replace the simple addition with a plugin-based sleep, or perhaps a synchronous network request that takes an extremely long time, wrapped in its own try/catch safety net.
I understand what you are trying to do. You don't want to kill the Javascript interpreter, you just want to prevent the form submission from proceeding.
HTML
<form id="myForm">
…
</form>
Javascript
// Setup…
var frm = document.getElementById('myForm'),
a = { value: 1 },
b = { value: 2 };
// Can change this code
var callFunc = function() {
// Throwing will do nothing here, since
// exceptions are being caught in a try/catch
// Instead, let's overwrite the submit handler with one that
// will cancel the form submission, then restore the old handler
var oldSubmitHandler = frm.submit;
var killHandler = function(e) {
// Prevents the submission
e.preventDefault();
// Restores the old handler
frm.submit = oldSubmitHandler;
};
frm.submit = killHandler;
};
// Can't change any of this code
if(a.value==1 && b.value==2)
{
try { callFunc() } catch(e) { }
}
// Want to stop this from happening
frm.submit();
See it in action: http://jsfiddle.net/3A7xC/
Better way is this:
if(a.value==1 && b.value==2)
{
try{
callFunc();
frm.submit();
}
catch(e) {
// stop execution
}
}
If an exception is thrown in function callFunc, the frm.submit(); line would not be executed. Instead, it will skip to the catch clause
Lots of answers, one more for fun.
You can put the code in a function, have the try block throw an error, then return from the catch clause:
function foo() {
var a = {value:1};
var b = {value:2};
if(a.value==1 && b.value==2) {
try {
callFunc();
} catch(e) {
alert(e.message);
return;
}
}
alert('error didn\'t stop me!');
}
function callFunc() {
throw new Error('This is an error.');
}
Otherwise you can set a flag in the catch block and test for it immediately afterward before going any further. Or take one of the other answer's options.
So the inside of the callFunc is the only thing you can change?
How about this:
callFunc(){
frm.submit(function() {
alert('this should not submit');
return false;
});
}
To kill the execution of a JS script use:
system.stop()
You can abort javascript execution using throw:
if(a.value==1 && b.value==2){
try{callFunc() }catch(e) {}
}
frm.submit();
function callFunc() {
throw "stop execution";
}
Related
I have a function:
function myfunction() {
if (a == 'stop') // How can I stop the function here?
}
Is there something like exit() in JavaScript?
You can just use return.
function myfunction() {
if(a == 'stop')
return;
}
This will send a return value of undefined to whatever called the function.
var x = myfunction();
console.log( x ); // console shows undefined
Of course, you can specify a different return value. Whatever value is returned will be logged to the console using the above example.
return false;
return true;
return "some string";
return 12345;
Apparently you can do this:
function myFunction() {myFunction:{
console.log('i get executed');
break myFunction;
console.log('i do not get executed');
}}
See block scopes through the use of a label: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/label
I can't see any downsides yet. But it doesn't seem like a common use.
Derived this answer: JavaScript equivalent of PHP’s die
function myfunction() {
if(a == 'stop')
return false;
}
return false; is much better than just return;
This:
function myfunction()
{
if (a == 'stop') // How can I stop working of function here?
{
return;
}
}
Using a little different approach, you can use try catch, with throw statement.
function name() {
try {
...
//get out of here
if (a == 'stop')
throw "exit";
...
} catch (e) {
// TODO: handle exception
}
}
if you are looking for a script to avoid submitting form when some errors found, this method should work
function verifyData(){
if (document.MyForm.FormInput.value.length == "") {
alert("Write something!");
}
else {
document.MyForm.submit();
}
}
change the Submit Button type to "button"
<input value="Save" type="button" onClick="verifyData()">
hope this help.
Using a return will stop the function and return undefined, or the value that you specify with the return command.
function myfunction(){
if(a=="stop"){
//return undefined;
return; /** Or return "Hello" or any other value */
}
}
I think throw a new error is good approach to stop execution rather than just return or return false. For ex. I am validating a number of files that I only allow max five files for upload in separate function.
validateMaxNumber: function(length) {
if (5 >= length) {
// Continue execution
}
// Flash error message and stop execution
// Can't stop execution by return or return false statement;
let message = "No more than " + this.maxNumber + " File is allowed";
throw new Error(message);
}
But I am calling this function from main flow function as
handleFilesUpload() {
let files = document.getElementById("myFile").files;
this.validateMaxNumber(files.length);
}
In the above example I can't stop execution unless I throw new Error.Just return or return false only works if you are in main function of execution otherwise it doesn't work.
I dislike answering things that aren't a real solution...
...but when I encountered this same problem, I made below workaround:
function doThis() {
var err=0
if (cond1) { alert('ret1'); err=1; }
if (cond2) { alert('ret2'); err=1; }
if (cond3) { alert('ret3'); err=1; }
if (err < 1) {
// do the rest (or have it skipped)
}
}
Hope it can be useful for anyone.
If you are using jquery. This should stop the function from bubbling up to so the parent function calling this should stop as well.
function myfunction(e)
{
e.stopImmediatePropagation();
................
}
exit(); can be use to go for the next validation.
type any random command that throws an error, for example:
exit
or
die:-)
How can Javascript duplicate the four-part try-catch-else-finally execution model that other languages support?
A clear, brief summary is from the Python 2.5 what's new. In Javascript terms:
// XXX THIS EXAMPLE IS A SYNTAX ERROR
try {
// Protected-block
} catch(e) {
// Handler-block
} else {
// Else-block
} finally {
// Final-block
}
The code in Protected-block is executed. If the code throws an exception, Handler-block is executed; If no exception is thrown, Else-block is executed.
No matter what happened previously, Final-block is executed once the code block is complete and any thrown exceptions handled. Even if there’s an error in Handler-block or Else-block and a new exception is raised, the code in Final-block is still run.
Note that cutting Else-block and pasting at the end of Protected-block is wrong. If an error happens in Else-block, it must not be handled by Handler-block.
I know this is old, but here is a pure syntax solution, which I think is the proper way to go:
try {
// Protected-block
try {
// Else-block
} catch (e) {
// Else-handler-block
}
} catch(e) {
// Handler-block
} finally {
// Final-block
}
The code in Protected-block is executed. If the code throws an error, Handler-block is executed; If no error is thrown, Else-block is executed.
No matter what happened previously, Final-block is executed once the code block is complete and any thrown errors handled. Even if there’s an error in Handler-block or Else-block, the code in Final-block is still run.
If an error is thrown in the Else-block it is not handled by the Handler-block but instead by the Else-handler-block
And if you know that the Else-block will not throw:
try {
// Protected-block
// Else-block
} catch(e) {
// Handler-block
} finally {
// Final-block
}
Moral of the story, don't be afraid to indent ;)
Note: this works only if the Else-handler-block never throws.
Extending the idea of jhs a little, the whole concept could be put inside a function, to provide even more readability:
var try_catch_else_finally = function(protected_code, handler_code, else_code, finally_code) {
try {
var success = true;
try {
protected_code();
} catch(e) {
success = false;
handler_code({"exception_was": e});
}
if(success) {
else_code();
}
} finally {
finally_code();
}
};
Then we can use it like this (very similar to the python way):
try_catch_else_finally(function() {
// protected block
}, function() {
// handler block
}, function() {
// else block
}, function() {
// final-block
});
I know the question is old and answers has already given but I think that my answer is the simplest to get an "else" in javascripts try-catch-block.
var error = null;
try {
/*Protected-block*/
} catch ( caughtError ) {
error = caughtError; //necessary to make it available in finally-block
} finally {
if ( error ) {
/*Handler-block*/
/*e.g. console.log( 'error: ' + error.message );*/
} else {
/*Else-block*/
}
/*Final-block*/
}
Javascript does not have the syntax to support the no-exception scenario. The best workaround is nested try statements, similar to the "legacy" technique from PEP 341
// A pretty-good try/catch/else/finally implementation.
try {
var success = true;
try {
protected_code();
} catch(e) {
success = false;
handler_code({"exception_was": e});
}
if(success) {
else_code();
}
} finally {
this_always_runs();
}
Besides readability, the only problem is the success variable. If protected_code sets window.success = false, this will not work. A less readable but safer way uses a function namespace:
// A try/catch/else/finally implementation without changing variable bindings.
try {
(function() {
var success = true;
try {
protected_code();
} catch(e) {
success = false;
handler_code({"exception_was": e});
}
if(success) {
else_code();
}
})();
} finally {
this_always_runs();
}
Here's another solution if the problem is the common one of not wanting the error callback to be called if there is an uncaught error thrown by the first callback. ... i.e. conceptually you want ...
try {
//do block
cb(null, result);
} catch(err) {
// err report
cb(err)
}
But an error in the success cb causes the problem of cb getting called a second time. So instead I've started using
try {
//do block
try {
cb(null, result);
} catch(err) {
// report uncaught error
}
} catch(err) {
// err report
cb(err)
}
which is a variant on #cbarrick's solution.
Let's say I have this code:
var myVar = 0;
function myFunctionOne() {
myVar = myVar + 2;
if(myVar <= 3) {
alert("all is good");
} else {
showError(myVar);
}
}
function myFunctionTwo() {
myVar = myVar + 2;
if(myVar <= 3) {
alert("all is good");
} else {
showError(myVar);
}
}
function myFunctionThree() {
//This should never run....
myVar = myVar + 2;
if(myVar <= 3) {
alert("all is good");
} else {
showError(myVar);
}
}
function showError(myVar) {
alert("Error Var is larger than 3. Var is" + myVar);
return false;
//This doesn't seem to stop anything
}
myFunctionOne();
myFunctionTwo();
myFunctionThree();
Here is also the fiddle: http://jsfiddle.net/dzjk44Lr/
What can I put inside my showError() function, that will kill any subsequent function calls? In this example, myFunctionThree(); should never run.
I know this is a simple example, but I'm trying to get my head around the module pattern, and in my module I have a lot of functions that delegate work, and modify variables. So if one function fails, or is given an illegal variable, I want everything to stop and show the user an error. Because if there was an error in myFunctionOne() for example, there is no point in continuing to execute any of the other code.
I guess, I'm looking for something like the php exit() function.
Any advice about how to do this, or how I should do it differently would be greatly appreciated.
You can throw an error:
throw new Error("Error Var is larger than 3. Var is" + myVar);
You can use javascript throw statement.
According to Mozilla MDN
Execution of the current function will stop (the statements after throw won't be executed), and control will be passed to the first catch block in the call stack. If no catch block exists among caller functions, the program will terminate.
Example:
throw "An error ocurred."
You can also go pro and throw an error object like this:
throw new MyAppError("custom error str", 128);
How can Javascript duplicate the four-part try-catch-else-finally execution model that other languages support?
A clear, brief summary is from the Python 2.5 what's new. In Javascript terms:
// XXX THIS EXAMPLE IS A SYNTAX ERROR
try {
// Protected-block
} catch(e) {
// Handler-block
} else {
// Else-block
} finally {
// Final-block
}
The code in Protected-block is executed. If the code throws an exception, Handler-block is executed; If no exception is thrown, Else-block is executed.
No matter what happened previously, Final-block is executed once the code block is complete and any thrown exceptions handled. Even if there’s an error in Handler-block or Else-block and a new exception is raised, the code in Final-block is still run.
Note that cutting Else-block and pasting at the end of Protected-block is wrong. If an error happens in Else-block, it must not be handled by Handler-block.
I know this is old, but here is a pure syntax solution, which I think is the proper way to go:
try {
// Protected-block
try {
// Else-block
} catch (e) {
// Else-handler-block
}
} catch(e) {
// Handler-block
} finally {
// Final-block
}
The code in Protected-block is executed. If the code throws an error, Handler-block is executed; If no error is thrown, Else-block is executed.
No matter what happened previously, Final-block is executed once the code block is complete and any thrown errors handled. Even if there’s an error in Handler-block or Else-block, the code in Final-block is still run.
If an error is thrown in the Else-block it is not handled by the Handler-block but instead by the Else-handler-block
And if you know that the Else-block will not throw:
try {
// Protected-block
// Else-block
} catch(e) {
// Handler-block
} finally {
// Final-block
}
Moral of the story, don't be afraid to indent ;)
Note: this works only if the Else-handler-block never throws.
Extending the idea of jhs a little, the whole concept could be put inside a function, to provide even more readability:
var try_catch_else_finally = function(protected_code, handler_code, else_code, finally_code) {
try {
var success = true;
try {
protected_code();
} catch(e) {
success = false;
handler_code({"exception_was": e});
}
if(success) {
else_code();
}
} finally {
finally_code();
}
};
Then we can use it like this (very similar to the python way):
try_catch_else_finally(function() {
// protected block
}, function() {
// handler block
}, function() {
// else block
}, function() {
// final-block
});
I know the question is old and answers has already given but I think that my answer is the simplest to get an "else" in javascripts try-catch-block.
var error = null;
try {
/*Protected-block*/
} catch ( caughtError ) {
error = caughtError; //necessary to make it available in finally-block
} finally {
if ( error ) {
/*Handler-block*/
/*e.g. console.log( 'error: ' + error.message );*/
} else {
/*Else-block*/
}
/*Final-block*/
}
Javascript does not have the syntax to support the no-exception scenario. The best workaround is nested try statements, similar to the "legacy" technique from PEP 341
// A pretty-good try/catch/else/finally implementation.
try {
var success = true;
try {
protected_code();
} catch(e) {
success = false;
handler_code({"exception_was": e});
}
if(success) {
else_code();
}
} finally {
this_always_runs();
}
Besides readability, the only problem is the success variable. If protected_code sets window.success = false, this will not work. A less readable but safer way uses a function namespace:
// A try/catch/else/finally implementation without changing variable bindings.
try {
(function() {
var success = true;
try {
protected_code();
} catch(e) {
success = false;
handler_code({"exception_was": e});
}
if(success) {
else_code();
}
})();
} finally {
this_always_runs();
}
Here's another solution if the problem is the common one of not wanting the error callback to be called if there is an uncaught error thrown by the first callback. ... i.e. conceptually you want ...
try {
//do block
cb(null, result);
} catch(err) {
// err report
cb(err)
}
But an error in the success cb causes the problem of cb getting called a second time. So instead I've started using
try {
//do block
try {
cb(null, result);
} catch(err) {
// report uncaught error
}
} catch(err) {
// err report
cb(err)
}
which is a variant on #cbarrick's solution.
I have a function:
function myfunction() {
if (a == 'stop') // How can I stop the function here?
}
Is there something like exit() in JavaScript?
You can just use return.
function myfunction() {
if(a == 'stop')
return;
}
This will send a return value of undefined to whatever called the function.
var x = myfunction();
console.log( x ); // console shows undefined
Of course, you can specify a different return value. Whatever value is returned will be logged to the console using the above example.
return false;
return true;
return "some string";
return 12345;
Apparently you can do this:
function myFunction() {myFunction:{
console.log('i get executed');
break myFunction;
console.log('i do not get executed');
}}
See block scopes through the use of a label: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/label
I can't see any downsides yet. But it doesn't seem like a common use.
Derived this answer: JavaScript equivalent of PHP’s die
function myfunction() {
if(a == 'stop')
return false;
}
return false; is much better than just return;
This:
function myfunction()
{
if (a == 'stop') // How can I stop working of function here?
{
return;
}
}
Using a little different approach, you can use try catch, with throw statement.
function name() {
try {
...
//get out of here
if (a == 'stop')
throw "exit";
...
} catch (e) {
// TODO: handle exception
}
}
if you are looking for a script to avoid submitting form when some errors found, this method should work
function verifyData(){
if (document.MyForm.FormInput.value.length == "") {
alert("Write something!");
}
else {
document.MyForm.submit();
}
}
change the Submit Button type to "button"
<input value="Save" type="button" onClick="verifyData()">
hope this help.
Using a return will stop the function and return undefined, or the value that you specify with the return command.
function myfunction(){
if(a=="stop"){
//return undefined;
return; /** Or return "Hello" or any other value */
}
}
I think throw a new error is good approach to stop execution rather than just return or return false. For ex. I am validating a number of files that I only allow max five files for upload in separate function.
validateMaxNumber: function(length) {
if (5 >= length) {
// Continue execution
}
// Flash error message and stop execution
// Can't stop execution by return or return false statement;
let message = "No more than " + this.maxNumber + " File is allowed";
throw new Error(message);
}
But I am calling this function from main flow function as
handleFilesUpload() {
let files = document.getElementById("myFile").files;
this.validateMaxNumber(files.length);
}
In the above example I can't stop execution unless I throw new Error.Just return or return false only works if you are in main function of execution otherwise it doesn't work.
I dislike answering things that aren't a real solution...
...but when I encountered this same problem, I made below workaround:
function doThis() {
var err=0
if (cond1) { alert('ret1'); err=1; }
if (cond2) { alert('ret2'); err=1; }
if (cond3) { alert('ret3'); err=1; }
if (err < 1) {
// do the rest (or have it skipped)
}
}
Hope it can be useful for anyone.
If you are using jquery. This should stop the function from bubbling up to so the parent function calling this should stop as well.
function myfunction(e)
{
e.stopImmediatePropagation();
................
}
exit(); can be use to go for the next validation.
type any random command that throws an error, for example:
exit
or
die:-)