# Circular Buffer A circular buffer, cyclic buffer or ring buffer is a data structure that uses a single, fixed-size buffer as if it were connected end-to-end. A circular buffer first starts empty and of some predefined length. For example, this is a 7-element buffer: [ ][ ][ ][ ][ ][ ][ ] Assume that a 1 is written into the middle of the buffer (exact starting location does not matter in a circular buffer): [ ][ ][ ][1][ ][ ][ ] Then assume that two more elements are added — 2 & 3 — which get appended after the 1: [ ][ ][ ][1][2][3][ ] If two elements are then removed from the buffer, the oldest values inside the buffer are removed. The two elements removed, in this case, are 1 & 2, leaving the buffer with just a 3: [ ][ ][ ][ ][ ][3][ ] If the buffer has 7 elements then it is completely full: [6][7][8][9][3][4][5] When the buffer is full an error will be raised, alerting the client that further writes are blocked until a slot becomes free. The client can opt to overwrite the oldest data with a forced write. In this case, two more elements — A & B — are added and they overwrite the 3 & 4: [6][7][8][9][A][B][5] Finally, if two elements are now removed then what would be returned is not 3 & 4 but 5 & 6 because A & B overwrote the 3 & the 4 yielding the buffer with: [ ][7][8][9][A][B][ ] ## Setup Go through the setup instructions for JavaScript to install the necessary dependencies: http://exercism.io/languages/javascript/installation ## Making the Test Suite Pass Execute the tests with: jasmine .spec.js Replace `` with the name of the current exercise. E.g., to test the Hello World exercise: jasmine hello-world.spec.js In many test suites all but the first test have been skipped. Once you get a test passing, you can unskip the next one by changing `xit` to `it`. ## Source Wikipedia [http://en.wikipedia.org/wiki/Circular_buffer](http://en.wikipedia.org/wiki/Circular_buffer) ## Submitting Incomplete Solutions It's possible to submit an incomplete solution so you can see how others have completed the exercise.