if (event && event.source && event.source.postMessage) { return queue; } 7. For context of what went wrong with it, the printer was giving error B200, and the troubleshooting instructions I found online suggested cleaning the printhead but didnt specify the ratio of alcohol to water, so I looked for better cleaning instructions and found yours. if (window.__uspapi === uspStubFunction && uspTries < uspTriesLimit) { } My printhead is soaking as we speak. json = JSON.parse(event.data); How to I set my printer to print in gray scale or black and white only? res['headjs'] = ''; dids_do[slot] = slot_lsa_indx+1; I have the very problem that you describe. var xmlhttp; Connected printer with wireless and reinstalled same driver. res['bodyjs'] = '