Can global constants be declared in JavaScript?
Javascript doesn't really have the notion of a named constant, or an immutable property of an object. (Note that I'm not talking about ES5 here.)
You can declare globals with a simple var
declaration in the global scope, like outside any function in a script included by a web page:
<script>
var EXACTLY_ONE = 1;
Then your code can use that constant of course, though it's not really "constant" because the value can be changed (the property updated, in other words).
edit — this is an ancient answer to an ancient question. In 2019, there's the const
declaration that's supported just about everywhere. However note that like let
, const
scoping is different from var
scoping.
As "Pointy" so carefully notes, ECMAscript has no such feature. However, JavaScript does:
const a = 7;
document.writeln("a is " + a + ".");
Of course, if you're writing code to put on the web to run in web browsers, this might not help you much. :-)