Customize Publish functionality in Experience Editor

I want to add a custom condition for Publishing an item in Experience Editor Mode.
By default it uses the Publish.js and in that JS, there is function as below:

showPublishDialog: function(context) {
      ExperienceEditor.modifiedHandling(true, function (isOk) {
        ExperienceEditor.PipelinesUtil.initAndExecutePipeline(context.app.PublishPipeline, context);

What is this context.app.PublishPipeline, how can I abort publish pipeline based on condition?