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    4.1.5 • Public • Published


    100% compliant, self-hosted javascript parser with high focus on both performance and stability. Stable and already used in production.

    Meriyah NPM GitHub license Total alerts Circle License



    • Conforms to the standard ECMAScript® 2021 (ECMA-262 11th 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

    Note: These features need to be enabled with the next option.


    npm install meriyah --save-dev


    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, end offsets and range: [start, end] to each node
      ranges: false;
      // Enable web compatibility
      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

    onComment and onToken

    If an array is supplied, comments/tokens will be pushed to the array, the item in the array contains start/end/range information when ranges flag is true, it will also contain loc information when loc flag is true.

    If a function callback is supplied, the signature must be

    function onComment(type: string, value: string, start: number, end: number, loc: SourceLocation): void {}
    function onToken(token: string, start: number, end: number, loc: SourceLocation): void {}

    Note the start/end/loc information are provided to the function callback regardless of the settings on ranges and loc flags. onComment callback has one extra argument value: string for the body string of the comment.

    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


    npm i meriyah

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