I found three ways to cast a variable to String
in JavaScript.
I searched for those three options in the jQuery source code, and they are all in use.
I would like to know if there are any differences between them:
value.toString()
String(value)
value + ""
They all produce the same output, but does one of them better than the others?
I would say the + ""
has an advantage that it saves some characters, but that's not that big advantage, anything else?
This question is related to
javascript
jquery
string
There are differences, but they are probably not relevant to your question. For example, the toString prototype does not exist on undefined variables, but you can cast undefined to a string using the other two methods:
?var foo;
?var myString1 = String(foo); // "undefined" as a string
var myString2 = foo + ''; // "undefined" as a string
var myString3 = foo.toString(); // throws an exception
On this page you can test the performance of each method yourself :)
http://jsperf.com/cast-to-string/2
here, on all machines and browsers, ' "" + str ' is the fastest one, (String)str is the slowest
They behave the same but toString
also provides a way to convert a number binary, octal, or hexadecimal strings:
Example:
var a = (50274).toString(16) // "c462"
var b = (76).toString(8) // "114"
var c = (7623).toString(36) // "5vr"
var d = (100).toString(2) // "1100100"
Real world example: I've got a log function that can be called with an arbitrary number of parameters: log("foo is {} and bar is {}", param1, param2)
. If a DEBUG
flag is set to true
, the brackets get replaced by the given parameters and the string is passed to console.log(msg)
. Parameters can and will be Strings, Numbers and whatever may be returned by JSON / AJAX calls, maybe even null
.
arguments[i].toString()
is not an option, because of possible null
values (see Connell Watkins answer)arguments[i] + ""
. This may or may not influence a decision on what to use. Some folks strictly adhere to JSLint.In addition to all the above, one should note that, for a defined value v
:
String(v)
calls v.toString()
'' + v
calls v.valueOf()
prior to any other type castSo we could do something like:
var mixin = {
valueOf: function () { return false },
toString: function () { return 'true' }
};
mixin === false; // false
mixin == false; // true
'' + mixin; // "false"
String(mixin) // "true"
Tested in FF 34.0 and Node 0.10
According to this JSPerf test, they differ in speed. But unless you're going to use them in huge amounts, any of them should perform fine.
For completeness: As asawyer already mentioned, you can also use the .toString()
method.
if you are ok with null, undefined, NaN, 0, and false all casting to '' then (s ? s+'' : '')
is faster.
see http://jsperf.com/cast-to-string/8
note - there are significant differences across browsers at this time.
Source: Stackoverflow.com