The V8 project aims to develop a high-performance, standards-compliant ECMAScript/JavaScript implementation. This document outlines our guidelines for “language-facing” changes and the process through which they are enforced.
We strive to be responsible stewards of JavaScript language, balancing interoperability and innovation. Our guidelines align closely with those of Blink project. Keep in mind that these are directional beacons, not bright-line rules.
Factors that reduce compatibility risk include:
In prioritizing the work of implementing new features, we will prefer those which unblock significant new capability, performance or expressiveness.
For every change we implement we want to validate our design and implementation every step of the way. As such, we aim to have a robust set of use cases for new features we implement; ideally, we want to be involved with the community, identifying groups of developers ready and willing to provide feedback for our implementations.
From day one, V8 has been all about performance. We strive to set standards for JavaScript performance across browsers, both by implementing advanced optimizations and by building robust benchmarks in our Octane benchmarking suite.
From a compatibility risk perspective, bugs and inadvertent incompatibilities in language implementations are very painful for users. Therefore we take special care to ensure high-quality implementations of JavaScript features we ship.
With this in mind, we expect all JavaScript changes implemented in V8 to be accompanied by:
As the implementation of a particular feature progresses, we expect both conformance and performance test suites to progress in parallel.
Language features implemented in V8 go over 3 stages: experimental implementation, staging, and shipping without a flag.
Anyone who wants to implement a feature in V8 must contact v8-users@googlegroups.com with an intent-to-implement e-mail. Then follow these steps:
At this stage, the feature becomes available in V8 under “--es-staging” flag. The criteria for moving a feature to that stage are:
As the implementation of a feature progresses, we will evaluate community feedback on feature design and implementation. V8 team will make a decision to turn the feature on by default based on community opinion of the feature and technical maturity of implementation.
Some community signals we will consider before shipment:
The following technical criteria must be met for shipping: