Use guard clauses to handle edge cases and failure conditions at the top of a function. Return immediately rather than nesting the happy path inside conditionals.
Good:
function process(data):
if data is null: return
if not data.is_valid(): return
return do_work(data)
Bad:
function process(data):
if data is not null:
if data.is_valid():
return do_work(data)
Apply this pattern where it genuinely makes the code cleaner — functions with clear precondition checks (null references, invalid parameters, boundary conditions) followed by main business logic as the happy path.
Only apply where it reduces complexity. Preserve simple if/else structures where they are already clear. Do not force the pattern into short functions where a single if/else is more readable, or when conditions represent legitimate alternative behaviors rather than failure cases.
References: