Early exit from function?

Question

I have a function:

function myfunction() {
  if (a == 'stop')  // How can I stop the function here?
}

Is there something like exit() in JavaScript?

Answer 1

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;

Answer 2

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

Answer 3

function myfunction() {
     if(a == 'stop') 
         return false;
}

return false; is much better than just return;

Answer 4

This:

function myfunction()
{
     if (a == 'stop')  // How can I stop working of function here?
     {
         return;
     }
}

Answer 5

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
    }
}

Answer 6

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.

Answer 7

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 */
    }
}

Answer 8

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.

Answer 9

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.

Answer 10

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();
       ................
  }

Answer 11

exit(); can be use to go for the next validation.

Answer 12

type any random command that throws an error, for example:

exit

or

die:-)