It can be a simple question here for many of you but for me it's a tough one!!
pos += 1 will increment the variable
pos by 1, and return it.
pos = +1 is the same as saying
pos = 1. The plus is redundant.
See it in action with this simple script:
pos1 = 10; pos2 = 10; pos1 += 1; pos2 =+ 1; console.log('pos1', pos1); console.log('pos2', pos2);