Cognitive Complexity

Cognitive Complexity is the measure of how difficult the code is to understand. It depends upon the breaks in the linear flow of the code and nesting. It also depends upon unnecessary return statements, jumps and other code smells that makes the code hard to be understood. Cognitive complexity does not accounts for execution speed or time complexity, it just signifies the code readability.

What adds to complexity?

When any function doesn't performs any loop and is executed from top to bottom without iteration it does not adds up to complexity. Below is an example of code without any cognitive complexity.

In the given function the flow is linear from top to bottom linearly therefore nothing contributes to the cognitive complexity.

Lets look into the same code written in some other form.

The function does the same thing as above but it has higher cognitive complexity as there is a loop involved and same lines of code are executed more than once.

Apart from loops, conditions, try/catch, logical expressions, jumps, recursion also adds to cognitive complexity.

Nesting of conditionals, loops and try/catch adds further more to cognitive complexity.

Note : Using code reduction techniques specific to any language does not add to cognitive complexity. For ex using arrow operator in JS (=>) to define a function instead of function keyword will not any complexity.

Reducing Cognitive Complexity

As a developer we should always make sure the code is easier to read as this is the thing that really makes a difference between an senior developer and someone who is starting new.

A function can be made easily readable by follow in some simple points.

• Break one function in case it is long into smaller functions and call them separately. Small written readable functions are always better than doing all logics in one function.
• No need to reassign value to variables when not needed.

• No need to use return when not required, it gives unnecessary break in the mind of person reading the code. For example in the below screenshot since it is IF-Else block, the return statement was not needed as anyway any one of the block was going to be executed being an if-else.

• No need to put == operators for Boolean variables check in if Condition.

• Give a proper comment to start of each function with function name, author , description and argument used in the function.
• No need to put continue; in a loop in case it is the last conditional statement of any loop.

There could be many ways in which the readability of a code can be increased and this is what cognitive complexity accounts for. It has no effect on performance rather just it is helpful in writing codes that are compact, easy to read and understand.