Unit 8 · Vibe coding with guardrails
Read AI-written code before you run it
A comment says what the code is meant to do; only the code says what it does. AI tools often write the comment first and the code second, and the two drift apart. Read each line, and treat any line you skip as one you are vouching for.
The mix-up
What people often think
“If the comment says it, the code does it.”
What the tutor says
Comments are notes, not guarantees. AI tools often write the comment first and the code second, and the two drift apart. Read the code.
How it works
Read the logic out loud. A filter that “hides items that do not match” but writes if (name.includes(term)) item.hidden = true hides the matches. Better names will not fix that; the condition needs its !.
Lines you do not understand are not harmless boilerplate. A fetch to an unfamiliar address sends data across the internet; find out whose server it is before you run it.
Side by side
// hide items that do not match the search
if (name.includes(term)) item.hidden = true;// hide items that do not match the search
item.hidden = !name.includes(term);Close cousins of this mix-up
The tutor watches for these in the same lesson.
“Lines I do not understand are probably harmless boilerplate.”
A line you skip is a line you are vouching for. fetch sends data across the internet; that is never filler.
“If the code works, there is nothing to explain.”
Working today is not the same as understood. A one-line comment proves you know why it works, and helps whoever edits it next, including the AI.
“Clearer names make the code correct.”
A good name helps the next reader, but the logic still hides the matches. Read the hidden line out loud: it hides an item when it does include the term.
Practise it with a tutor watching
Read before you run
Explain what each block of AI-generated code does, and catch the line that does the opposite of what it claims.
Free with an account. The first two units need no account.