nsISupports
Last changed in Gecko 1.8 (Firefox 1.5 / Thunderbird 1.5 / SeaMonkey 1.0)Version strings are dot-separated sequences of version-parts. A version-part consists of up to four parts, all of which are optional:
<number-a><string-b><number-c><string-d (everything else)>
A version-part may also consist of a single asterisk "*" which indicates * "infinity". Numbers are base-10, and are zero if left out. Strings are compared bytewise.
For additional backwards compatibility, if "string-b" is "+" then "number-a" is incremented by 1 and "string-b" becomes "pre".
1.0pre1 < 1.0pre2 < 1.0 == 1.0.0 == 1.0.0.0 < 1.1pre == 1.1pre0 == 1.0+ < 1.1pre1a < 1.1pre1 < 1.1pre10a < 1.1pre10
Implemented by: @mozilla.org/xpcom/version-comparator;1
. The service can be accessed directly via Services.vc
after loading Services.jsm
or with the following code:
var versionComparator = Components.classes["@mozilla.org/xpcom/version-comparator;1"] .getService(Components.interfaces.nsIVersionComparator);
Method overview
long compare(in ACString A, in ACString B); |
Methods
compare()
Compare two version strings.
long compare( in ACString A, in ACString B );
Parameters
-
A
- The first version.
-
B
- The second version.
Return value
If A
and B
are two version being compared, and the return value
- is smaller than 0, then A < B
- equals 0 then Version, then A==B
- is bigger than 0, then A > B
Example
function compareVersions(a,b) { var x = Services.vc.compare(a,b); if(x == 0) return a + "==" + b; else if(x > 0) return a + ">" + b; return a + "<" + b; } dump(compareVersions("1.0pre", "1.0"));
Example - Compare current browser version
This example here uses nsIXULAppInfo component to get the version of the browser that the code is running in. See here: nsIXULAppInfo
Components.utils.import("resource://gre/modules/Services.jsm"); var curentBrowserVersion =Services.appinfo.platformVersion; //example: '31.*' var compareToThisVersion = '25.*';
var compareResult =Services.vc.compare(curentBrowserVersion,
if (compareResult == -1) { //currentBrowserVersion is less than '25.*' (compareToThisVersion) } else if (compareResult == 0) { //currentBrowserVersion is '25.*' (compareToThisVersion) } else if (compareResult == 1) { //currentBrowserVersion is greater than '25.*' (compareToThisVersion) } else { //will never get here as Services.vc.compare only returns -1, 0, or 1 }compareToThisVersion
);