7

I realized I've been switching between them with no understanding as to why, and am finding it hard to search for.

Cœur
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expiredninja
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    Can you make a specific example? – Pekka Jun 01 '12 at 14:59
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    Strings can use either `""` or `''`, it doesn't matter (pick the one that makes you need to escape less (`"Mr. O'Neil"` or `'I said "hi"'`). Numbers don't need to be quoted, eg. `12`. – gen_Eric Jun 01 '12 at 15:00

4 Answers4

16

' ' and " " are the same thing; they are used to define string literals.

Things without quotes can be an identifier, keyword, non-string literal, property name or a number (may have missed one).

Examples:

"hello world"        literal (string)
'hello world'        literal (string) with same contents
document             identifier (object)
{ a: 1 }             property name
if                   keyword (start conditional statement)
3.4                  literal (number)
/abc/                literal (regex object)

String literals that are enclosed in single quotes don't need escaped double quotes and visa versa, e.g.:

'<a href="">click me</a>'    HTML containing double quotes
"It's going to rain"         String containing single quote
Ja͢ck
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    The last two wouldn't really be considered identifiers, would they? Seems to me they're the literal syntax of their individual types (number and regular expression), just like the first two string examples. –  Jun 01 '12 at 15:10
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    @amnotiam you make a valid point; i've reclassified them as literals :) thanks! – Ja͢ck Jun 01 '12 at 15:14
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    Ah, there we are. +1 Only other things (that I can think of) under the category of *stuff without quotes* would be operators and statement terminators... and I suppose whitespace if you want to count that. –  Jun 01 '12 at 15:19
  • @amnotiam hehe quite right, but I think this will have to do for now unless OP wants a full language break down ;-) – Ja͢ck Jun 01 '12 at 15:22
  • Yeah, you've already covered what OP was asking, and much more. –  Jun 01 '12 at 15:23
6

' ' and " " used to quote string literal and represents string(s) whereas literal without quote are variables (name of variable, constant) know as identifier, example

variable = 'Hello'; (Here `variable` is identifier and 'Hello' is string literal)


var = "Ho There"

You might question, what is the difference between ' (single quote) and " (Double quote)

Difference is ,strings within " if have special character then they need to escape. Example:

Variable = "hi " there"; ---> here you need to escape the " inside string like

Variable = "hi \" there";

But if using, ' then no need of escaping (unless there is a extra ' in string). You can hve like

var = 'Hello " World"';
Rahul
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5

" and ' are interchangeable (but need to be used together).

myObject["property"] and myObject.property are also interchangeable. $var foo = "property"; myObject[foo] as well (per comment below).

djechlin
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0

A quick jsfiddle around and both single and double quotes escape control codes etc.

In latter days I have had errors from HTML where double quotes have not been used, and if you look at the spec for JSON you'll note it is a double quote that is asked for when quoting string literals. So it is double quotes that is the convention I think, for historical reasons.

However! In these days of writing server side JS I must admit I tend to be pulled back to my C roots and double quote where I want escaped chars and single quote strings that are effectively literal chars and never likely to contain escaped chars (even though this is essentially non-productive behaviour). Besides which most of my JS is coffeescript nowadays anyway, nobody ever wrote javascript for elegance, CS is a different kettle of fish though.

user5321531
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