# jsx-ast-utils
AST utility module for statically analyzing JSX.
## Installation
```sh
$ npm i jsx-ast-utils --save
```
## Usage
This is a utility module to evaluate AST objects for JSX syntax. This can be super useful when writing linting rules for JSX code. It was originally in the code for [eslint-plugin-jsx-a11y](https://github.com/evcohen/eslint-plugin-jsx-a11y), however I thought it could be useful to be extracted and maintained separately so **you** could write new interesting rules to statically analyze JSX.
### ESLint example
```js
import { hasProp } from 'jsx-ast-utils';
// OR: var hasProp = require('jsx-ast-utils').hasProp;
// OR: const hasProp = require('jsx-ast-utils/hasProp');
// OR: import hasProp from 'jsx-ast-utils/hasProp';
module.exports = context => ({
JSXOpeningElement: node => {
const onChange = hasProp(node.attributes, 'onChange');
if (onChange) {
context.report({
node,
message: `No onChange!`
});
}
}
});
```
## API
### AST Resources
1. [JSX spec](https://github.com/facebook/jsx/blob/master/AST.md)
2. [JS spec](https://github.com/estree/estree/blob/master/spec.md)
### hasProp
```js
hasProp(props, prop, options);
```
Returns boolean indicating whether an prop exists as an attribute on a JSX element node.
#### Props
Object - The attributes on the visited node. (Usually `node.attributes`).
#### Prop
String - A string representation of the prop you want to check for existence.
#### Options
Object - An object representing options for existence checking
1. `ignoreCase` - automatically set to `true`.
2. `spreadStrict` - automatically set to `true`. This means if spread operator exists in
props, it will assume the prop you are looking for is not in the spread.
Example: `` looking for specific prop here will return false if `spreadStrict` is `true`.
### hasAnyProp
```js
hasAnyProp(props, prop, options);
```
Returns a boolean indicating if **any** of props in `prop` argument exist on the node.
#### Props
Object - The attributes on the visited node. (Usually `node.attributes`).
#### Prop
Array - An array of strings representing the props you want to check for existence.
#### Options
Object - An object representing options for existence checking
1. `ignoreCase` - automatically set to `true`.
2. `spreadStrict` - automatically set to `true`. This means if spread operator exists in
props, it will assume the prop you are looking for is not in the spread.
Example: `` looking for specific prop here will return false if `spreadStrict` is `true`.
### hasEveryProp
```js
hasEveryProp(props, prop, options);
```
Returns a boolean indicating if **all** of props in `prop` argument exist on the node.
#### Props
Object - The attributes on the visited node. (Usually `node.attributes`).
#### Prop
Array - An array of strings representing the props you want to check for existence.
#### Options
Object - An object representing options for existence checking
1. `ignoreCase` - automatically set to `true`.
2. `spreadStrict` - automatically set to `true`. This means if spread operator exists in
props, it will assume the prop you are looking for is not in the spread.
Example: `` looking for specific prop here will return false if `spreadStrict` is `true`.
### getProp
```js
getProp(props, prop, options);
```
Returns the JSXAttribute itself or undefined, indicating the prop is not present on the JSXOpeningElement.
#### Props
Object - The attributes on the visited node. (Usually `node.attributes`).
#### Prop
String - A string representation of the prop you want to check for existence.
#### Options
Object - An object representing options for existence checking
1. `ignoreCase` - automatically set to `true`.
### elementType
```js
elementType(node)
```
Returns the tagName associated with a JSXElement.
#### Node
Object - The visited JSXElement node object.
### getPropValue
```js
getPropValue(prop);
```
Returns the value of a given attribute. Different types of attributes have their associated values in different properties on the object.
This function should return the most *closely* associated value with the intention of the JSX.
#### Prop
Object - The JSXAttribute collected by AST parser.
### getLiteralPropValue
```js
getLiteralPropValue(prop);
```
Returns the value of a given attribute. Different types of attributes have their associated values in different properties on the object.
This function should return a value only if we can extract a literal value from its attribute (i.e. values that have generic types in JavaScript - strings, numbers, booleans, etc.)
#### Prop
Object - The JSXAttribute collected by AST parser.
### propName
```js
propName(prop);
```
Returns the name associated with a JSXAttribute. For example, given `` and the JSXAttribute for `foo`, this will return the string `"foo"`.
#### Prop
Object - The JSXAttribute collected by AST parser.