estree VS kataw

ESLint's AST format, ESTree, would represent this line of code as:

That was a super interesting link, thank you.

For the ontological problem, I presume you're referring to how there are so many differing ideas of how to represent ASTs (apologies for mixing languages, these URLs were just handy):

* https://lisperator.net/uglifyjs/ast#nodes

* https://github.com/estree/estree#the-estree-spec

* ... likely others

which makes it hard for ls1 to ask ls2 about "the for-of iteration variable Node" because ls2 could be using UglifyJS or ESTree or their own(!) AST nomenclature?

And all of this is made worse by (e.g.) Java1.3 versus Java19 because languages are rarely static

I find it better to actually look at the AST for javascript.

These are expressions:

https://github.com/estree/estree/blob/master/es5.md#expressi...

These are statements:

https://github.com/estree/estree/blob/master/es5.md#statemen...

I guess the confusing part for many is how an expression can also be a statement. But if you look at the ExpressionStatement you see that an expression is not also a statement. It's just the wrapper statement!

When I started the NodeSecure project I had almost no experience 🐤 with AST (Abstract Syntax Tree). My first time was on the SlimIO project to generate codes dynamically with the astring package (and I had also looked at the ESTree specification).

ESTree compatible output, AST explorer on WASM

The parser we wrote transforms the GraphQL AST into ESTree structure, so it allows you to travel the GraphQL AST tree easily.

For espree parser(the one eslint uses) we can refer here Eslint AST Node Types

It then builds on the assumption that all of Javascript performance scales linearly based on the results of that fishy benchmark. Never mind that in C you can stack allocate, or use arena allocators, or use a million of other tricks, where in JS, once you write {}, you got a heap allocation that you don't have any control over (and if you think this doesn't matter, this is one of the reasons why esbuild is so much faster than babel, or heck even kataw, the fastest JS parsing toolkit I'm aware of).

esbuild is the current darling leading the pack, but there are also various other projects in the space (swc[0] is written in Rust, fjb[1] is written in C, bun[2] is written in zig, leveraging JavascriptCore's engine).

The most significant performance-oriented effort in this space still leveraging JS that I know of is kataw[3], and while that's quite fast compared to babel, it's still within an order of magnitude from babel. Kataw itself is a CST-based implementation that was created to outperform seafox (a AST-based parser by the same developer).

Babel gained popularity due to the crazy amount of churn in grammar over the past few years, but more and more I think the dust is settling, and flexibility is no longer the name of the game, making an AST-based implementation less appealing. The Rome team must be feeling the heat if the data structure design choices are being informed by performance. I highly doubt someone will be able to compete in performance using a JS implementation in today's landscape.

[0] https://github.com/swc-project/swc

[1] https://github.com/sebbekarlsson/fjb

[2] https://bun.sh/

[3] https://github.com/kataw/kataw

Kataw is a *work in progress* javascript toolchain with high focus on performance, and it's main goal is to unify functionality that has previously been separate tools. It's core is an ECMAScript friendly CST that allows you to parse `ECMAScript® 2022 (ECMA-262 12th Edition) language specification`. Each CST node contains several properties, and the `flags` property contains the CST info. The CST info can be extracted from the CST node through public API methods. Click [here](https://github.com/kataw/kataw/tree/main/src/parser#public-api-methods-to-extract-info-from-cst-nodes) for a complete list over all the public API methods. Many of these APIs have the advantage that they allow you to "retrieve" info that is not otherwise available with a standard AST parser. One example is that you only need to use `kataw.isStatementNode` to find out if the current CST node is a statement node. With an AST parser you must use a `switch statement` with 60 `switch cases`. Another example is how easy it is to find out if a keyword node contains an `escaped keyword`. You only need to use `kataw.hasUnicodeEscape`. You can narrow this down further if you use `kataw.isChildLess`. A keyword doesn't have any child nodes. A third benefit with this CST parser is that it is running in `recovery mode` by `default` and can be used in any editor. A build-in diagnostic system reports diagnostics if an `error handler` have been used. The diagnostics are dynamic. It means all the diagnostics are informative, and they will will change based on the context you are parsing in. The diagnostics have been designed like this so you can quickly understand what the problem is and correct it. These features used together gives you more options to adjust, modify and customize the CST tree compared to a regular AST parser and you can also write fewer code lines and at the same time experience insane performance.