Parse and allowlist URL schemes
See this course’s project requirements
A defensive local link-directory app with text-only rendering, allowed URL schemes, same-origin explanation and a validation matrix using inert fictional strings.
Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.
What to include
- Demonstrate literal rendering of markup-like label text using fixed DOM structure.
- Produce a parser-versus-policy matrix for accepted HTTPS and rejected scheme/relative cases.
- Show embedded-credential rejection and distinguish address validation from destination review.
- Create an origin tuple comparison and a correct browser-access boundary explanation.
- Retain inert validation tests, literal-render observations, and unchanged-list rejection evidence.
- Deliver the tested local directory with explicit implemented rules and unimplemented security boundaries.
Review and revise
Use these criteria to check your work and choose what to improve.
- The implementation or declared simulation follows the supplied contract and retains inspectable original inputs.
- Normal, boundary and rejected cases are recorded with expected versus observed results.
- The changed case has a correct explanation and does not rely on hidden state.
- The project includes source, outputs, instructions and honest tool, privacy and verification limits.
Want more background?
The idea in everyday life
Use directory.html, link-rules.mjs and test-links.mjs with label <b>Guide</b> and https://example.com/help. Serve locally with python3 -m http.server 8765 --bind 127.0.0.1. The markup-like label is inert text; do not follow external links during practice.
The URL parser identifies components; an explicit scheme rule decides which parsed URLs this app accepts. Successful parsing alone is not approval.
Parse and allowlist URL schemes — original worked practice
The URL parser identifies components; an explicit scheme rule decides which parsed URLs this app accepts. Successful parsing alone is not approval.
Use directory.html, link-rules.mjs and test-links.mjs with label <b>Guide</b> and https://example.com/help. Serve locally with python3 -m http.server 8765 --bind 127.0.0.1. The markup-like label is inert text; do not follow external links during practice.
1. Step 1
Read allowedURL: construct new URL(raw), then require https: and no username/password.
You should see: Parsing and approval are separate stages.
The URL parser identifies components; an explicit scheme rule decides which parsed URLs this app accepts. Successful parsing alone is not approval.
2. Step 2
Try https://example.com/help and inspect the normalized accepted URL.
You should see: The harmless absolute HTTPS example is accepted.
The URL parser identifies components; an explicit scheme rule decides which parsed URLs this app accepts. Successful parsing alone is not approval.
3. Step 3
Try the inert string javascript:alert(1) without activating it.
You should see: The scheme rule rejects it before an anchor is created.
The URL parser identifies components; an explicit scheme rule decides which parsed URLs this app accepts. Successful parsing alone is not approval.
4. Step 4
Record accepted/rejected schemes and the reason for each.
You should see: A URL scheme validation matrix.
The URL parser identifies components; an explicit scheme rule decides which parsed URLs this app accepts. Successful parsing alone is not approval.
What to finish
Produce a parser-versus-policy matrix for accepted HTTPS and rejected scheme/relative cases.
Watch for this
Equating successful URL parsing with an approved destination or approved scheme.
How can I tell I understand it?
Demonstrate the rule: The URL parser identifies components; an explicit scheme rule decides which parsed URLs this app accepts. Successful parsing alone is not approval. Use the supplied variant to distinguish a changed result from a broken implementation.
Quick knowledge check
Answer all 3 questions. Get at least 2 right and the lesson completes automatically.
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Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.
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Source & access notes · checked 2026-10-01
Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.
Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.
Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.
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