index.js
function done() {
        var arg = errors.length ? errors : null
        --pending || process.nextTick(callback, arg)
    }
function done() {
        var arg = errors.length ? errors : null
        --pending || process.nextTick(callback, arg)
    }
function done ( ) { var arg = errors . length ? errors : null -- pending || process . nextTick ( callback , arg ) }
helper for counting finished operations and call back when we're done
helper for counting finished operations and call back when we re done