Welcome to WebmasterWorld Guest from 50.16.112.199

Forum Moderators: open

javascript purpose of semicolon?

dumb question

   
7:30 pm on Aug 6, 2003 (gmt 0)

10+ Year Member




Hi,

Never realized this before. A javascript expression doesn't have to end with a ';'.

So what's the diffrence? For example, between
alert("1") & alert("1");

This kind of things are so hard to find through search engines:).

7:37 pm on Aug 6, 2003 (gmt 0)

10+ Year Member



it programming, one usually indicates the end of a statement with a semi-colon. Some langauges, such as c or c++, demand it.

Javascript, on the other hand, does not demand it, so if you don't want to put it, then don't.

8:07 pm on Aug 6, 2003 (gmt 0)

WebmasterWorld Senior Member tedster is a WebmasterWorld Top Contributor of All Time 10+ Year Member



When writing or editing javascript, the semicolon helps a lot visually.

Depending on your editor, it may not be clear otherwise if you actually have a line break in there (ending the line of code). Instead, your editor may just be wrapping the line visually. So without the semicolon, you can make and overlook errors more easily.

10:18 pm on Aug 6, 2003 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member



Semicolen is a formally necessary part of JavaScript statements:

[mozilla.org...]
[mozilla.org...]

Practically speaking, it is not needed in most cases. The browser can usually parse statements based on new-lines, line-breaks and other informal conventions.

It is a good idea to put it anyways, though, because for example, a person may have the option to use strict JS in Mozilla turned on, and they might get syntax warnings in the console without it.

Also, in certain cases (e.g., in a bookmarklet) the lack of the semicolen may cause the evaluation of the statement to fail because there is no new-line or space or line-break between two statements (e.g.,

var a="Henry the ",b=7;++b;alert(a+b+"th\nI am, I am...");
).

Jordan

10:23 pm on Aug 6, 2003 (gmt 0)

WebmasterWorld Senior Member g1smd is a WebmasterWorld Top Contributor of All Time 10+ Year Member Top Contributors Of The Month



If you have multiple, or nested, IF ... THEN ... ELSE statements and you miss off a semi-colon then the code may do something different to what you were expecting in some browsers.
10:36 pm on Aug 6, 2003 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member



g1smd:

I had something similar happen just the other day actually, lol. I switch()'d a value and in one of the cases I forgot the semicolen after the break statement, doh. Took me like an hour to figure out what was wrong with it.

Jordan

gph

10:45 pm on Aug 6, 2003 (gmt 0)

10+ Year Member



MonkeeSage I did exactly the same thing a couple weeks ago :) I stared at it for ages. I'm not condoning it but I only use semicolons if I have to. It's a bad habit that shows up in things like switch()
12:59 pm on Aug 7, 2003 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member



I believe they're also required if you have more than one statement per line. (for those who like to eliminate all possible redundant whitespace to reduce file sizes)
1:29 pm on Aug 7, 2003 (gmt 0)

WebmasterWorld Senior Member korkus2000 is a WebmasterWorld Top Contributor of All Time 10+ Year Member



It is required for multiple statements on one line. If you want to save space by combining lines then the semicolon lets the parser know it is a new statement. On some browsers the semicolon is required for multiple commands inside of one command structure.

if(y=0){
alert("yes");
y=1;
}

Some parsers need the semicolon or you get an error because it runs the to statements together.

3:42 pm on Aug 7, 2003 (gmt 0)

10+ Year Member



korkus,

what space are you saving? in your example, at worst case, you're only saving 6 or 9 bytes (3 CRLF pairs and maybe 3 space characters)...

3:49 pm on Aug 7, 2003 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member



I think that'd be visual space, i.e. line count

SN

 

Featured Threads

My Threads

Hot Threads This Week

Hot Threads This Month