Grater
Grater is an ECMAScript abstract syntax trees (AST) Parser, according to The ESTree Spec
What is an Abstract syntax tree (AST)?
Abstract syntax trees are data structures widely used in compilers, due to their property of representing the structure of program code. An AST is usually the result of the syntax analysis phase of a compiler.
It's too early to release the source files to the public, but get a taste of it. Here
📝 Feature To-Do List
- ES5
- RegularExpressionLiteral
- HoistableDeclaration
- LabelStatement
- ES6/ES2015 & More ES Feature
- Scope
- JSX Expressions
- More test cases covered & running Test262
- Support TC39 proposals via options
💡 What the Grater can be used for?
- Parse Javascript
- Syntax checker
- Lint
- Convert the syntax of different ECMA versions
- Global API for performing AST operations and tree walkers
Install
# yarn
yarn add grater
# npm
npm install graterUsage
import { parseScript } from 'grater';
parseScript(`
Array.prototype.customReduce = function (fn, initialValue) {
// fn(acc, cur, ?index, ?originArray)
var sourceArray = this;
var acc, currentIndex
if(initialValue) {
acc = initialValue
currentIndex = 0
} else {
acc = sourceArray[0]
currentIndex = 1
}
while(currentIndex < sourceArray.length) {
var currentValue = sourceArray[currentIndex]
acc = fn(acc, currentValue, currentIndex, sourceArray)
currentIndex ++
}
return acc;
};
`);AST in JSON
{
"type": "Program",
"sourceType": "script",
"body": [
{
"type": "ExpressionStatement",
"expression": {
"type": "AssignmentExpression",
"left": {
"type": "MemberExpression",
"object": {
"type": "MemberExpression",
"object": {
"type": "Identifier",
"name": "Array"
},
"computed": false,
"property": {
"type": "Identifier",
"name": "prototype"
}
},
"computed": false,
"property": {
"type": "Identifier",
"name": "customReduce"
}
},
"operator": "=",
"right": {
"type": "FunctionExpression",
"id": null,
"params": [
{
"type": "Identifier",
"name": "fn"
},
{
"type": "Identifier",
"name": "initialValue"
}
],
"body": {
"type": "BlockStatement",
"body": [
{
"type": "VariableDeclaration",
"kind": "var",
"declarations": [
{
"type": "VariableDeclarator",
"id": {
"type": "Identifier",
"name": "sourceArray"
},
"init": {
"type": "ThisExpression"
}
}
]
},
{
"type": "VariableDeclaration",
"kind": "var",
"declarations": [
{
"type": "VariableDeclarator",
"id": {
"type": "Identifier",
"name": "acc"
},
"init": null
},
{
"type": "VariableDeclarator",
"id": {
"type": "Identifier",
"name": "currentIndex"
},
"init": null
}
]
},
{
"type": "IfStatement",
"test": {
"type": "Identifier",
"name": "initialValue"
},
"consequent": {
"type": "BlockStatement",
"body": [
{
"type": "ExpressionStatement",
"expression": {
"type": "AssignmentExpression",
"left": {
"type": "Identifier",
"name": "acc"
},
"operator": "=",
"right": {
"type": "Identifier",
"name": "initialValue"
}
}
},
{
"type": "ExpressionStatement",
"expression": {
"type": "AssignmentExpression",
"left": {
"type": "Identifier",
"name": "currentIndex"
},
"operator": "=",
"right": {
"type": "Literal",
"value": 0
}
}
}
]
},
"alternate": {
"type": "BlockStatement",
"body": [
{
"type": "ExpressionStatement",
"expression": {
"type": "AssignmentExpression",
"left": {
"type": "Identifier",
"name": "acc"
},
"operator": "=",
"right": {
"type": "MemberExpression",
"object": {
"type": "Identifier",
"name": "sourceArray"
},
"computed": true,
"property": {
"type": "Literal",
"value": 0
}
}
}
},
{
"type": "ExpressionStatement",
"expression": {
"type": "AssignmentExpression",
"left": {
"type": "Identifier",
"name": "currentIndex"
},
"operator": "=",
"right": {
"type": "Literal",
"value": 1
}
}
}
]
}
},
{
"type": "WhileStatement",
"test": {
"type": "BinaryExpression",
"left": {
"type": "Identifier",
"name": "currentIndex"
},
"right": {
"type": "MemberExpression",
"object": {
"type": "Identifier",
"name": "sourceArray"
},
"computed": false,
"property": {
"type": "Identifier",
"name": "length"
}
},
"operator": "<"
},
"body": {
"type": "BlockStatement",
"body": [
{
"type": "VariableDeclaration",
"kind": "var",
"declarations": [
{
"type": "VariableDeclarator",
"id": {
"type": "Identifier",
"name": "currentValue"
},
"init": {
"type": "MemberExpression",
"object": {
"type": "Identifier",
"name": "sourceArray"
},
"computed": true,
"property": {
"type": "Identifier",
"name": "currentIndex"
}
}
}
]
},
{
"type": "ExpressionStatement",
"expression": {
"type": "AssignmentExpression",
"left": {
"type": "Identifier",
"name": "acc"
},
"operator": "=",
"right": {
"type": "CallExpression",
"callee": {
"type": "Identifier",
"name": "fn"
},
"arguments": [
{
"type": "Identifier",
"name": "acc"
},
{
"type": "Identifier",
"name": "currentValue"
},
{
"type": "Identifier",
"name": "currentIndex"
},
{
"type": "Identifier",
"name": "sourceArray"
}
]
}
}
},
{
"type": "ExpressionStatement",
"expression": {
"type": "UpdateExpression",
"argument": {
"type": "Identifier",
"name": "currentIndex"
},
"operator": "++",
"prefix": false
}
}
]
}
},
{
"type": "ReturnStatement",
"argument": {
"type": "Identifier",
"name": "acc"
}
}
]
},
"async": false,
"generator": false
}
}
}
]
}