breaking a while loop with return

[jimfog]

I am using a loop to iterate through an array and break from it when an IF statement is satisfied...

In the code you will see...when the IF statement is satisfied I use return to exit from the function and from the loop...and after that I use break.

 

I think break though is redundant...you tell me for sure:

    compare_dts:function(col){                 var tfrom=$('#timesfrom').val(),ttill=$('#timestill').val();                 var i=0;                 var s=new Date(col.models[i].attributes.start);                 var e=new Date(col.models[i].attributes.end);                 while (i < col.models.length) {                 i++;                 var st=s.getTime()/1000,en=e.getTime()/1000;                   if((st==tfrom)&&(en==ttill))                   {    $('.pack_check').html('blabla...').css( "color", "red" );                      return false;                        break;//does this have to go away?                                                          }                   else                   {$('.pack_check').html('');                    return}                 }                    },

As the code currently is...there is no problem,I want to be sure anyway though.

 

The purpose(anyway) is that when this IF condition is met the functions returns false.

[davej]

Your while loop appears to repeat the same instructions for no good reason.

 

Perhaps you can explain what it is supposed to accomplish?

[justsomeguy]

Right, that loop is just going to execute the same piece of code over and over, it won't do anything different each time through the loop other than increment i. It doesn't look like there's a reason for the loop. To answer the original question, code after a return statement does not get executed.

[jimfog]

That loop goes through an array.This array might have 3 elements(for example)...each element is an object and 2 of the object's attributes are start and end.

 

The logic is this:

If some of these attributes meet a condition(see the if statement) then the loop must stop.

 

 

There may be a case where the condition is not met,in such a scenario the loop will just end.

 

So why do you say that there is no reason in repeating the instructions.

The loop is there to find something(that is why is there the if condition) in the array.

[justsomeguy]

Look at what it does:

while (i < col.models.length) {  i++;  var st=s.getTime()/1000,en=e.getTime()/1000;  if((st==tfrom)&&(en==ttill))  {    $('.pack_check').html('blabla...').css( "color", "red" );    return false;  }  else  {    $('.pack_check').html('');    return;  }}

The loop will continue as long as i is less than col.models.length. First, it increments i. Then it gets s.getTime and e.getTime. Then it compares those with tfrom and ttill, and either way it will return and the loop ends after the first run.But even if those return statements were gone, it would still be doing the same thing every time through the loop. The data it works with is s.getTime, e.getTime, tfrom, and ttill. None of those variables change inside the loop, the only variable that changes inside the loop is i, and you don't use i anywhere else in the loop. So you could run that loop 100 times and it's going to do the same thing 100 times: get s.getTime and e.getTime, and compare them with tfrom and ttill. None of those values changes during the loop, it will always use the same values. That's why the loop is not necessary, there's no point to doing the exact same calculations and comparisons with the same values over and over.

[jimfog]

Look at what it does:

while (i < col.models.length) {  i++;  var st=s.getTime()/1000,en=e.getTime()/1000;  if((st==tfrom)&&(en==ttill))  {    $('.pack_check').html('blabla...').css( "color", "red" );    return false;  }  else  {    $('.pack_check').html('');    return;  }}

The loop will continue as long as i is less than col.models.length. First, it increments i. Then it gets s.getTime and e.getTime. Then it compares those with tfrom and ttill, and either way it will return and the loop ends after the first run.But even if those return statements were gone, it would still be doing the same thing every time through the loop. The data it works with is s.getTime, e.getTime, tfrom, and ttill. None of those variables change inside the loop, the only variable that changes inside the loop is i, and you don't use i anywhere else in the loop. So you could run that loop 100 times and it's going to do the same thing 100 times: get s.getTime and e.getTime, and compare them with tfrom and ttill. None of those values changes during the loop, it will always use the same values. That's why the loop is not necessary, there's no point to doing the exact same calculations and comparisons with the same values over and over.

 

You are right in what you say...the way the loop is now it is rather useless...

 

So...take a look at this:

   while (i < col.models.length) {                 var s=new Date(col.models[i].attributes.start);                 var e=new Date(col.models[i].attributes.end);                 var st=s.getTime()/1000,en=e.getTime()/1000;                   if((st==tfrom)&&(en==ttill))                   {                                      $('.pack_check').html('bla blah').css( "color", "red" );                      return false;                                        }                    i++;                 }

Τell me what you think now..as I said before...the logic is that the loop searches through an array and when something is found(if condition) the loop stops.

 

If nothing is found then the loop ends-after it has searched through all the array.

[Ingolme]

That looks correct, but I can't tell for sure, what are the chances that the values of st and en are exactly equal to the values of tfrom and ttill? The number has millisecond precision, if it's off by just one millisecond the condition will return false.

 

I assume after the loop you'll be returning true, otherwise the person calling the function is going to get a value that always evaluates to false.

[jimfog]

 

 

I assume after the loop you'll be returning true, otherwise the person calling the function is going to get a value that always evaluates to false.

Υes I fixed that...