Download db.js (666 bytes)
Mozzila convinced in 2010 the W3C not to develop the standard as the only implementation was SQLite. As a consequence, Firefox intentionally didn't include the support and later Safari abandoned theirs. Luckily, WebKit maintains it for more than a decade since then, and other vendors seem to follow them as implementing SQLite is relatively easy and very useful. Let's hope the public pressure will revive the W3C standard.
WebSQL is implemented with asynchronous interface, which DB simplifies by utilizing Promises: modern approach to parallel programming in Javascript. The simplicity comes at cost of transactions, which can be easily understood from the source code.