esutils

What is esutils?

The esutils npm package is a utility library for ECMAScript language tools. It provides various utility functions to help with the manipulation and validation of ECMAScript (JavaScript) code.

What are esutils's main functionalities?

AST (Abstract Syntax Tree) Validation

This feature allows you to validate if a string is a valid ECMAScript identifier, keyword, or reserved word.

const esutils = require('esutils');
let isValidIdentifier = esutils.keyword.isIdentifierName('myIdentifier'); // true

Code Generation

This feature helps in determining if a string is a reserved word in ECMAScript for a given version.

const esutils = require('esutils');
let isReservedWord = esutils.keyword.isReservedWord('super', 6); // true

Literal Analysis

This feature provides functions to analyze literals in the AST, such as checking if a node is a string literal.

const esutils = require('esutils');
let isStringLiteral = esutils.ast.isStringLiteral({ type: 'Literal', value: 'Hello' }); // true

Other packages similar to esutils

acorn

Acorn is a small, fast, JavaScript-based JavaScript parser. It provides a similar AST-related utility but with a focus on parsing JavaScript code into an AST.

estraverse

Estraverse is a library for traversing and updating the AST. It is similar to esutils in that it deals with ASTs but focuses more on traversal and modification rather than validation.

jshint

JSHint is a tool that helps to detect errors and potential problems in JavaScript code. While it is not a utility library like esutils, it performs validation of JavaScript code, which is one of the functionalities provided by esutils.

README

esutils

esutils (esutils) is utility box for ECMAScript language tools.

API

ast

ast.isExpression(node)

Returns true if node is an Expression as defined in ECMA262 edition 5.1 section 11.

ast.isStatement(node)

Returns true if node is a Statement as defined in ECMA262 edition 5.1 section 12.

ast.isIterationStatement(node)

Returns true if node is an IterationStatement as defined in ECMA262 edition 5.1 section 12.6.

ast.isSourceElement(node)

Returns true if node is a SourceElement as defined in ECMA262 edition 5.1 section 14.

ast.trailingStatement(node)

Returns Statement? if node has trailing Statement.

if (cond)
    consequent;

When taking this IfStatement, returns consequent; statement.

ast.isProblematicIfStatement(node)

Returns true if node is a problematic IfStatement. If node is a problematic IfStatement, node cannot be represented as an one on one JavaScript code.

{
    type: 'IfStatement',
    consequent: {
        type: 'WithStatement',
        body: {
            type: 'IfStatement',
            consequent: {type: 'EmptyStatement'}
        }
    },
    alternate: {type: 'EmptyStatement'}
}

The above node cannot be represented as a JavaScript code, since the top level else alternate belongs to an inner IfStatement.

code

code.isDecimalDigit(code)

Return true if provided code is decimal digit.

code.isHexDigit(code)

Return true if provided code is hexadecimal digit.

code.isOctalDigit(code)

Return true if provided code is octal digit.

code.isWhiteSpace(code)

Return true if provided code is white space. White space characters are formally defined in ECMA262.

code.isLineTerminator(code)

Return true if provided code is line terminator. Line terminator characters are formally defined in ECMA262.

code.isIdentifierStart(code)

Return true if provided code can be the first character of ECMA262 Identifier. They are formally defined in ECMA262.

code.isIdentifierPart(code)

Return true if provided code can be the trailing character of ECMA262 Identifier. They are formally defined in ECMA262.

keyword

keyword.isKeywordES5(id, strict)

Returns true if provided identifier string is a Keyword or Future Reserved Word in ECMA262 edition 5.1. They are formally defined in ECMA262 sections 7.6.1.1 and 7.6.1.2, respectively. If the strict flag is truthy, this function additionally checks whether id is a Keyword or Future Reserved Word under strict mode.

keyword.isKeywordES6(id, strict)

Returns true if provided identifier string is a Keyword or Future Reserved Word in ECMA262 edition 6. They are formally defined in ECMA262 sections 11.6.2.1 and 11.6.2.2, respectively. If the strict flag is truthy, this function additionally checks whether id is a Keyword or Future Reserved Word under strict mode.

keyword.isReservedWordES5(id, strict)

Returns true if provided identifier string is a Reserved Word in ECMA262 edition 5.1. They are formally defined in ECMA262 section 7.6.1. If the strict flag is truthy, this function additionally checks whether id is a Reserved Word under strict mode.

keyword.isReservedWordES6(id, strict)

Returns true if provided identifier string is a Reserved Word in ECMA262 edition 6. They are formally defined in ECMA262 section 11.6.2. If the strict flag is truthy, this function additionally checks whether id is a Reserved Word under strict mode.

keyword.isRestrictedWord(id)

Returns true if provided identifier string is one of eval or arguments. They are restricted in strict mode code throughout ECMA262 edition 5.1 and in ECMA262 edition 6 section 12.1.1.

keyword.isIdentifierNameES5(id)

Return true if provided identifier string is an IdentifierName as specified in ECMA262 edition 5.1 section 7.6.

keyword.isIdentifierNameES6(id)

Return true if provided identifier string is an IdentifierName as specified in ECMA262 edition 6 section 11.6.

keyword.isIdentifierES5(id, strict)

Return true if provided identifier string is an Identifier as specified in ECMA262 edition 5.1 section 7.6. If the strict flag is truthy, this function additionally checks whether id is an Identifier under strict mode.

keyword.isIdentifierES6(id, strict)

Return true if provided identifier string is an Identifier as specified in ECMA262 edition 6 section 12.1. If the strict flag is truthy, this function additionally checks whether id is an Identifier under strict mode.

License

Copyright (C) 2013 Yusuke Suzuki (twitter: @Constellation) and other contributors.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.