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Possible Duplicate:
Difference between single quotes and double quotes in Javascript

Sorry guys, but here I am asking a stupid question. In Javascript, do we use " or ' ?

Looking at the code below, it seems that " and ' behave differently?

var html = '<dt> <img src="' + imageurl + '" /> </dt>';

Can somebody explain to me the different between " and ' ?

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Vennsoh
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    Exact copy of http://stackoverflow.com/questions/3149192/difference-between-single-quotes-and-double-quotes-in-javascript – Emre Yazici Jul 03 '11 at 22:46
  • If both " and ' are identical and no different. When I do something like var html = "
    "; In Dreamweaver it gives me error? Is that an IDE problem?     – Vennsoh Jul 03 '11 at 23:02
  • Read the other answers here. You can't use the double quote to delimit your string and then include double quotes in that string unless you escape the embedded double quote. My answer below gives you examples of these scenarios. – jfriend00 Jul 03 '11 at 23:05
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    @Vennsoh: As the answer in the links and below indicate, you need to alternate between the two in order to nest them, or you need to escape the nested ones. In your example, the first `"` starts a string literal, and the next `"` closes the string literal. You'd need to escape the second `"\" /> "`, or change it to a single `"' /> "`. – user113716 Jul 03 '11 at 23:07

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In javascript there is no difference. Both are valid for enclosing a string i.e. defining a string literal.

Your example shows double quotation marks that are a value inside a string. They are clearly part of markup that is held in that string. Their presence is unrelated to the javascript language, and that string could equivalently have been defined:

var html = "<dt> <img src=\"" + imageurl + "\" /> </dt>";

Usually the only reason one is chosen over the other is convenience. For example, when quoting markup (as in your example) there are often many double quotes (although single quotes are just as valid), so it's easier to define the string with single quotes, and not have to escape slash every quote that should be part of the string (as oppose to defining the string's boundaries).

On the other hand, free text often contains many apostrophes, in which case it's often easier to enclose the string with double quotes: "It'll be easier this way, that'll save me some work".

davin
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It depends on what you open and close with.

A ' will end on the next detected ' and a " will end on the next detected "

Your example could also be written:

var html = "<dt> <img src='" + imageurl + "' /> </dt>";

There is no difference, it just depends on what you open with

Dan Hanly
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You can use either form of quote. These are identical:

var html1 = "<bold>Hi</bold>";
var html2 = '<bold>Hi</bold>';

Whichever delimiter you choose to start the string with, the next unescaped occurrence of that delimiter signals the end of the string.

Where life gets interesting is when there are embedded quote marks in your string itself. For example, supposed you want to assign this to a javascript variable:

<img src="http://www.google.com/images/logo1w.png">

In that case, you a couple choices. You could use this which escapes the embedded double quotes:

var html1 = "<img src=\"http://www.google.com/images/logo1w.png\">";

or you can use this:

var html2 = '<img src="http://www.google.com/images/logo1w.png">';

I find that the latter looks a lot cleaner.

jfriend00
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You can use single or double quotes to enclose an expression. As long as the same type of quote closes the expression, all is good.

If you plan on including HTML in the string, you should use single quotes... that way you don't have to escape the double quotes.

If you used double quotes in the above, you would need to escape the inside quotes, eg.

var html = "<dt> <img src=\"" + imageurl + "\" /> </dt>";

Jason Gennaro
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In javascript, they are the same. You can switch between them for easier escaping of potential quotes in the string literal itself.

Be careful, because in some other languages (like perl) there is a difference: in that case, double quoted string would allow variable interpolation, while single quoted strings would not. Javascript at present does not support this feature.

Joel Coehoorn
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