Front-end JavaScript reviewProgramming Training

JavaScript code review for front-end projects

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JavaScript code review for front-end projects

Example result

Example for the Standard package

Code review: Python order-import script for a small online shop

What the code does

  1. Reads orders.csv from the shop export.
  2. For each order line, finds the product by SKU in stock.xlsx and subtracts the quantity.
  3. Writes the updated stock back and logs totals to import_log.txt.

The structure is clear and functions are well named. Most issues are about input that does not look the way the script expects.

Bugs and weak spots

#LineSeverityIssue
148HighThe same CSV can be imported twice; there is no check for already processed order IDs. This is the most likely cause of negative stock.
272Highint(row["qty"]) crashes on empty or "2.0" values from refunded orders.
395MediumSKU lookup is case-sensitive: "gt-101" and "GT-101" are treated as different products.
4130MediumThe file is opened without encoding="utf-8", so product names with accents break on Windows.
5201LowBare except: hides real errors and makes the log useless.

Corrected fragments

Issue 1: skip orders already imported

processed = load_processed_ids("processed_orders.txt")
for row in reader:
    if row["order_id"] in processed:
        continue
    # ... existing logic ...
    processed.add(row["order_id"])
save_processed_ids("processed_orders.txt", processed)

Why: each order is applied once, even if you run the script on the same file again.

Issue 2: read quantity safely

raw = (row.get("qty") or "").strip()
try:
    qty = int(float(raw))
except ValueError:
    log.warning("Order %s: bad quantity %r, skipped", row["order_id"], raw)
    continue

Why: refunded or partial lines are skipped with a clear note instead of stopping the whole import.

Issue 3: normalise SKUs

sku = row["sku"].strip().upper()

Apply the same .strip().upper() when building the stock dictionary.

Style and readability

  • process() is 90 lines long; split it into read_orders, apply_to_stock, write_report.
  • Replace magic column numbers (row[7]) with header names.

Please test each fix on a copy of your files: we read the code but did not run it.

Client: owner of a tea shop who wrote a 310-line Python script that imports orders from a CSV export into the stock spreadsheet Problem reported: "Sometimes stock goes negative, and the script crashes on some files."

The client and all details are made up.

About this service

Front-end JavaScript fails in quiet ways: an event listener added twice, a fetch call with no error handling, a comparison with == that lets the wrong value through, or a variable that leaks into global scope. We read your scripts, explain what runs when the page loads and when the user clicks, and mark the bugs and fragile spots. Fixes come as corrected fragments in modern JavaScript with notes on why they are safer.

What is included

  • What you getA written review on the order page with the order in which your code runs, a list of issues by importance and corrected fragments using let and const, async and await and clear event handling. Premium adds a short plan of what to restructure first.
  • Console errors explainedWhat the message really means
  • Events and the DOMListeners, selectors, timing
  • Async codePromises, fetch and error handling
  • Modern syntaxlet and const, === and modules
  • Fixed fragmentsWith a note on each change

How it works

  1. 1
    BriefYou paste the scripts and console errors
  2. 2
    ReadingWe trace what runs and when
  3. 3
    ReviewYou get the issues and fixed code

What we need from you

The JavaScript and the related HTML pasted as text or screenshots, the browser where it fails, what should happen and any errors from the browser console.

We will ask you:

  • Do you use plain JavaScript or a library?
  • In which browser does the problem appear?
  • What should happen on the page, and what happens instead?
  • Are there errors in the browser console?

Compare packages

PackagesBasicScript up to 100 lines$15StandardFront-end code up to 400 lines$35PremiumUp to 1,000 lines with a clean-up plan$69
Deadline1 day2 days3 days
Revisions123
Lines of codeup to 100up to 400up to 1,000
Corrected fragmentsYesYesYes
Clean-up planNoNoYes
Order BasicOrder StandardOrder Premium

Payment protection

You pay when you order, but the money is released only for accepted work.

  • Fixed priceThe package price does not change after you pay.
  • The money is reservedWhen you pay, the amount is only reserved. It is released to the service once you accept the work.
  • Checked before deliveryEvery result goes through a quality check before it reaches you, and you see it on the order page before accepting it.
  • Free revisionsAsk for changes within your brief as many times as the package allows.
  • Acceptance after 3 daysIf within 3 days of delivery you neither accept the work nor ask for changes, it is accepted automatically. If you write in the order chat after delivery, the order waits; once we answer, we may start the 3 days again and will say so in the chat.
  • Redo or a full refundIf the result does not match your brief and the revisions did not fix it, or the work takes more than twice its deadline, write in the order chat: we will redo the work or refund the payment in full.
How it works →

Questions and answers

Do you run my code?

No. We read it carefully and reason about how it behaves, but we do not execute it, so test every suggested fix in your own project.

Can you look at my live page instead?

Please paste the code itself. We review what you send and do not log in to your site or hosting.

Do you review React or Vue code here?

For React components there is a separate review focused on hooks and re-renders. Plain JavaScript, jQuery and small libraries fit this one best.

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Order · $35· 2 days