Jisubao Blog

How to Build a Website from Scratch (A No-Fluff Roadmap)

The three real paths (no-code, CMS, custom), the parts nobody mentions — domain, DNS, HTTPS, email — and when it's smarter to just hire someone.

Stop Using Math.random() for Secrets: How to Generate Truly Random Strings

Why Math.random() is a predictable PRNG unsafe for API keys, tokens and coupon codes — and how crypto.getRandomValues gives you strings nobody can guess, free in your browser.

How Many Days Between Two Dates? The Off-by-One Trap in Date Math

Why spreadsheet date subtraction drifts: time-of-day, time zones, leap years, and the elapsed-vs-inclusive off-by-one — plus a free browser-local calculator.

CSV to JSON: 6 Pitfalls That Silently Corrupt Your Data

Why zip codes lose their leading zeros, how a comma splits a row in half, semicolon delimiters, BOM characters — and how to convert safely in your browser.

What Is Base64? Why Your Image Becomes a Giant Text String

Base64 explained: why binary turns into long text, why it grows ~33%, why it is encoding not encryption, and how to encode/decode free.

Is Base64 Encoding Secure? What Online Decoders Can See

Base64 is encoding, not encryption — anyone can decode it. Learn what it protects, and why a private client-side decoder keeps your tokens off servers.

What Is URL Encoding? Why Spaces Become %20 and Chinese Turns to Garbled Text

Percent-encoding explained, why %20 and Chinese garble, the difference between encodeURI and encodeURIComponent, and how to convert free.

What Is a Unix Timestamp? Why Since 1970 and How to Convert

How timestamps work, 10-digit vs 13-digit, time-zone traps, and how to convert seconds and milliseconds free.

What Is JSON? How to Use the Online JSON Formatter

Understand the JSON format and use the free online tool to format, validate and prettify — copy and paste, ready to use.

Is Your Online JSON Formatter Leaking Your API Keys?

Why server-side formatters can upload your tokens, a real 2025 leak, and how to format JSON 100% in your browser — private, no account.

How to Create a Strong Password? Free Password Generator Guide

What a strong password is and why it matters; generate a high-entropy random password in one click, locally.

Can a Website See the Password You Generate?

Client-side vs server-side generators, how to check, and why a browser-local generator (Web Crypto) means we never see your password.

How QR Codes Work and How to Make One Free

What QR codes are for and how to turn text or a URL into a scannable code — download, no signup.

What Is a UUID? How to Generate One (v4) Free

UUIDs explained: what they are, GUID vs UUID, the v4 version, where they are used (keys, IDs, traces), and how to generate one locally.

What Is Markdown? How to Write & Preview It Free

Markdown explained: why developers and writers use it, the basic syntax, common mistakes, and how to preview it live.

What Is a Regular Expression? Test Regex Free

Regex explained: the core symbols, copy-paste patterns for email/phone/URL, the greedy trap, and how to test it live.

HEX to RGB: Convert Colors Instantly (Free)

HEX, RGB and HSL explained, why you convert between them, the simple math, and how to convert colors in one click.

How to Compare Two Texts: Free Online Diff Tool

What a diff is, line vs character mode, everyday uses (code review, drafts, config), and how to compare free.

How to Count Words & Characters Online (Free)

Why counts matter (tweets, essays, SEO meta), what gets counted, and how to count words and characters instantly.

3 Free Tools Every Cross-Border Seller Needs: FBA Profit, Title Optimization, FX Payout

Run the numbers before selling on Amazon: the FBA profit calculator, title length/keyword checker, and USD payout exchange tool—plus a sneak peek at our AI product-research tool.

Amazon US Referral Fee 2026 Quick Reference

Referral rates by category plus worked examples—calculate your commission cost before pricing, not by guesswork.

How Is the FBA Fulfillment Fee Calculated? Size Tiers, Rates & Pitfalls

Standard/oversize tier rules plus 2026 rate examples—avoid the 'heavy-item loss' trap, with a free calculator.

How to Write a Winning Amazon Title: Keyword Layout & Character Limits

200-character cap, core keyword in the first 80, brand + attribute + keyword formula—then check it in one click with the tool.

How to Scrape Data from a Website (Without Getting Blocked)

When scraping is allowed, the basic workflow, the blocks you'll hit (CAPTCHA, rate limits, anti-bot), and when to hire a pro.

How to Clean Messy Excel Data (Without Losing Rows)

The 7 most common CSV/Excel problems — dupes, whitespace, broken dates, encoding garbage — and a repeatable cleanup workflow.

Automate Repetitive Tasks with Python (Even If You're Not a Dev)

Which chores are worth automating, the building blocks, common traps, and when it pays to hire someone to build it.

How to Write a Blog Post with AI (Without the Robot Smell)

Use AI as a writing partner, not a ghostwriter: a practical workflow to draft faster, cut the robot tells, and keep your human voice.

How to Backtest a Trading Strategy (Without Fooling Yourself)

The workflow, what the metrics mean, and the 6 traps that inflate returns — look-ahead bias, overfitting, survivorship, hidden costs, data snooping, no out-of-sample test.