Guard clauses are a contract, not a shortcut
A guard clause is an explicit boundary for valid state, not a micro-optimization.
Judgment: Guard clauses are a correctness tool first; performance is incidental.
Guard clauses are not about speed. They are about declaring what must be true before the rest of the function is allowed to run.
Mechanism
A guard clause reduces the amount of valid state you have to reason about. When it exits early, it is defining the boundary of the function. That boundary is where you enforce correctness.
function publishPost(post) {
if (!post) return null
if (!post.title) return null
if (!post.body) return null
return store.publish(post)
}
This is a contract, not a shortcut. The contract is: no title, no body, no publish. The rest of the function never has to handle those invalid states.
Tradeoffs
Guard clauses can hide deeper invariants if you sprinkle them everywhere. Overuse makes the boundaries ambiguous. Use them where the boundary is real, not as a substitute for a proper validation layer.
Practical check
If removing the guard clause creates more than one new branch in the body, keep it. If it only saves a line or two, you are not asserting a boundary, you are just chasing style.