Writing custom Babel and ESLint plugins
Kent C. Dodds
Utah
1 wife, 3.5 kids
PayPal, Inc.
@kentcdodds
Please Stand...
... if you're physically able
What this talk is
- Basic introduction to the concept of ASTs
- (sorta) Practical demo of how to use ASTs with Babel and ESLint
- Something to get you totally psyched about using ASTs
What this talk is not
- A deep dive into parsing, tokenizing, and lexing
- Everything you need to know to be productive with ASTs
Let's
Get
STARTED!
Why
Should I care?
ESNext
ESNow
ESLint
eslint-plugin-import
Codemods
better than find/replace
no matter how good your regex skills are...
What
Is an AST?
Code for humans
const uniqueRandomArray = require('unique-random-array')
const transformersNames = require('./transformers-names.json')
const getRandomItem = uniqueRandomArray(transformersNames)
module.exports = {
all: transformersNames,
random: random,
}
function random(number) {
if (number === undefined) {
return getRandomItem()
} else {
const randomItems = []
for (let i = 0; i < number; i++) {
randomItems.push(getRandomItem())
}
return randomItems
}
}
Code for computers
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}Code for computers
For humans...
Exploring ASTs
For humans, for computers, for humans
How
Do I use them?
Let's try it out!
Resources
- JointJS: JavaScript AST Visualizer - jointjs.com/demos/javascript-ast
- Felix Kling: AST Explorer - astexplorer.net/
- Christoph Pojer: Evolving Complex Systems Incrementally | JSConf EU 2015 - kcd.im/jsconf-codemod-talk
- Ramana Venkata: How to write a codemod - kcd.im/codemod-tutorial
- Jamund Ferguson: Harnessing The Power of Abstract Syntax Trees - kcd.im/ast-power
- James Kyle: The Babel Plugin Handbook - kcd.im/babel-plugin-handbook
- James Kyle: How to Build a Compiler - kcd.im/compiler-talk
- ESLint: Working with Plugins - kcd.im/write-eslint-plugins
- ESTree "spec" - kcd.im/estree-spec
- "How Writing a Babel Plugin is like jQuery" - kcd.im/babel-query
- Babel Types Documentation - kcd.im/babel-types
Thank you!
Writing custom Babel and ESLint plugins
By Kent C. Dodds
Writing custom Babel and ESLint plugins
The Abstract Syntax Tree. It sounds a lot worse than it is. It’s actually quite simple and enables some powerful tools. BabelJS uses it to transform your code from ES.Next to ES5. ESLint uses it to lint your code. And with a knowledge of how it works, you can extend these and other tools to do some mind bustingly powerful things. Prepare to be amazed by ASTs!
