Increments the number stored at key by increment. If the key does not exist, it is set to zero before performing the operation.
|key||string||the key to increment|
|increment||number||the amount to increment by|
|Type||Resolves with||Rejected when|
|Promise<number>||On success, the promise resolves with the value of key after the increment.||If the key contains a value of the wrong type, or contains a string that cannot be represented as an integer, the promise is rejected with an error.|