Do you recommend using semicolons after every statement in JavaScript?

Solution 1:

Yes, you should use semicolons after every statement in JavaScript.

Solution 2:

An ambiguous case that breaks in the absence of a semicolon:

// define a function
var fn = function () {
    //...
} // semicolon missing at this line

// then execute some code inside a closure
(function () {
    //...
})();

This will be interpreted as:

var fn = function () {
    //...
}(function () {
    //...
})();

We end up passing the second function as an argument to the first function and then trying to call the result of the first function call as a function. The second function will fail with a "... is not a function" error at runtime.

Solution 3:

Yes, you should always use semicolons. Why? Because if you end up using a JavaScript compressor, all your code will be on one line, which will break your code.

Try http://www.jslint.com/; it will hurt your feelings, but show you many ways to write better JavaScript (and one of the ways is to always use semicolons).

Solution 4:

What everyone seems to miss is that the semi-colons in JavaScript are not statement terminators but statement separators. It's a subtle difference, but it is important to the way the parser is programmed. Treat them like what they are and you will find leaving them out will feel much more natural.

I've programmed in other languages where the semi-colon is a statement separator and also optional as the parser does 'semi-colon insertion' on newlines where it does not break the grammar. So I was not unfamiliar with it when I found it in JavaScript.

I don't like noise in a language (which is one reason I'm bad at Perl) and semi-colons are noise in JavaScript. So I omit them.

Solution 5:

I'd say consistency is more important than saving a few bytes. I always include semicolons.

On the other hand, I'd like to point out there are many places where the semicolon is not syntactically required, even if a compressor is nuking all available whitespace. e.g. at then end of a block.

if (a) { b() }