a mechanism to merge multiple coverage objects into one. Handles the use case of overlapping coverage information for the same files in multiple coverage objects and does not double-count in this situation. For example, if you pass the same coverage object multiple times, the final merged object will be no different that any of the objects passed in (except for execution counts).

The Collector is built for scale to handle thousands of coverage objects. By default, all processing is done in memory since the common use-case is of one or a few coverage objects. You can work around memory issues by passing in a Store implementation that stores temporary computations on disk (the tmp store, for example).

The getFinalCoverage method returns an object with merged coverage information and is provided as a convenience for implementors working with coverage information that can fit into memory. Reporters, in the interest of generality, should not use this method for creating reports.

Usage

 var collector = new require('istanbul').Collector();

 files.forEach(function (f) {
     //each coverage object can have overlapping information about multiple files
     collector.add(JSON.parse(fs.readFileSync(f, 'utf8')));
 });

 collector.files().forEach(function(file) {
     var fileCoverage = collector.fileCoverageFor(file);
     console.log('Coverage for ' + file + ' is:' + JSON.stringify(fileCoverage));
 });

 // convenience method: do not use this when dealing with a large number of files
 var finalCoverage = collector.getFinalCoverage();