Demo
Features
- Conforms to the standard ECMAScript® 2020 (ECMA-262 10th Edition) language specification
- Support TC39 proposals via option
- Support for additional ECMAScript features for Web Browsers
- JSX support via option
- Optionally track syntactic node locations
- Emits an ESTree-compatible abstract syntax tree.
- No backtracking
- Low memory usage
- Very well tested (~99 000 unit tests with full code coverage)
- Lightweight - ~90 KB minified
ESNext features
- Decorators
- Class Public Instance Fields & Private Instance Fields
- Hashbang grammar
- import.meta
- Nullish coalescing Operator
- Numeric separators
- Optional Chaining
- Private methods
- Static class fields and private static methods
Note: These features need to be enabled with the next option.
Installation
npm install meriyah --save-dev
API
Meriyah generates AST according to ESTree AST format, and can be used to perform syntactic analysis (parsing) of a JavaScript program, and with ES2015 and later a JavaScript program can be either a script or a module.
The parse method exposed by meriyah takes an optional options object which allows you to specify whether to parse in script mode (the default) or in module mode.
This is the available options:
{
// The flag to allow module code
module: false;
// The flag to enable stage 3 support (ESNext)
next: false;
// The flag to enable start and end offsets to each node
ranges: false;
// Enable web compability
webcompat: false;
// The flag to enable line/column location information to each node
loc: false;
// The flag to attach raw property to each literal and identifier node
raw: false;
// Enabled directives
directives: false;
// The flag to allow return in the global scope
globalReturn: false;
// The flag to enable implied strict mode
impliedStrict: false;
// Allows comment extraction. Accepts either a function or array
onComment: []
// Allows token extraction. Accepts either a function or array
onToken: []
// Enable non-standard parenthesized expression node
preserveParens: false;
// Enable lexical binding and scope tracking
lexical: false;
// Adds a source attribute in every node’s loc object when the locations option is `true`
source: false;
// Distinguish Identifier from IdentifierPattern
identifierPattern: false;
// Enable React JSX parsing
jsx: false
// Allow edge cases that deviate from the spec
specDeviation: false
}
Example usage:
import { parseScript } from './meriyah';
parseScript('({x: [y] = 0} = 1)');
This will return when serialized in json:
{
type: "Program",
sourceType: "script",
body: [
{
type: "ExpressionStatement",
expression: {
type: "AssignmentExpression",
left: {
type: "ObjectPattern",
properties: [
{
type: "Property",
key: {
type: "Identifier",
name: "x"
},
value: {
type: "AssignmentPattern",
left: {
type: "ArrayPattern",
elements: [
{
"type": "Identifier",
"name": "y"
}
]
},
right: {
type: "Literal",
value: 0
}
},
kind: "init",
computed: false,
method: false,
shorthand: false
}
]
},
operator: "=",
right: {
type: "Literal",
value: 1
}
}
}
]
}