Node/ExpressJS Can’t Set Headers Bug…Possible solution

February 1, 2015
Reading Time: 1 minute

I was working on some of my more complex project aspects today, after spending an entire weekend setting up, and building out most of my applications unit and end-to-end tests when I noticed this issue when I moved onto the new build features inside of the Angular app:

Possibly unhandled Error: Can’t set headers after they are sent.

I’m scouring the code EVERYWHERE. How is this possible? According to my unit tests, I have code coverage across all of these functions with literally every permutation¬†of tests imaginable, or did I???

Upon further inspection, I noticed that my AngularJS front end was making two identical calls to my API. This simultaneous connection request was enough to throw the error in the Node/ExpressJS backend.

tl:dr; – Check to be sure your AngularJS / Front End isn’t making simultaneous calls incorrectly to your API/Backend.

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