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- eval-estree-expression
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Readme
eval-estree-expression 
Safely evaluate JavaScript (estree) expressions, sync and async.
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(TOC generated by verb using markdown-toc)
Install
Install with npm :
$ npm install --save eval-estree-expressionUsage
Evaluates an estree expression from [@babel/parser][], esprima, acorn, or any other library that parses and returns a valid estree expression.
const { evaluate } = require('eval-estree-expression');
evaluate(expressionTree[, context]); // async
evaluate.sync(expressionTree[, context]); // syncSee the unit tests for hundreds of additional usage examples.
Params
The evaluate function takes the following arguments:
expressionTree{object} - a valid estree expression AST.context{object} - a data object with values to replace variables in expressions
Usage with Babel
Most of the examples in this document assume the following setup code is used:
const { evaluate } = require('eval-estree-expression');
const { parseExpression } = require('@babel/parser');
// parse your JavaScript expression
const ast = parseExpression('1 + 2);
// evaluate synchronously
console.log(evaluate.sync(ast)); //=> 3
// or asynchronously
console.log(await evaluate(ast)); //=> 3Usage with Esprima
[Esprima][esprimar] doesn't have a "parseExpression" method like @babel/parser, so you'll need to return the expression from the AST, like so:
const { parse } = require('esprima');
const { evaluate } = require('eval-estree-expression');
const ast = parse('[1, 2, 3].map(n => n * x);').body[0].expression;
// evaluate synchronously
console.log(evaluate.sync(ast)); // =>, [2, 4, 6]
// or asynchronously
console.log(await evaluate(ast)); // =>, [2, 4, 6]async usage
Evaluate expresssions asynchronously.
console.log(await evaluate(parse('1 + 2'))); //=> 3
console.log(await evaluate(parse('5 * 2'))); //=> 10
console.log(await evaluate(parse('1 > 2'))); //=> false
console.log(await evaluate(parse('1 < 2'))); //=> true
// with context object
console.log(await evaluate(parse('page.title === "home"'), { page: { title: 'home' } })); //=> truesync usage
Evaluate expresssions synchronously.
console.log(evaluate.sync(parse('1 + 2'))); //=> 3
console.log(evaluate.sync(parse('5 * 2'))); //=> 10
console.log(evaluate.sync(parse('1 > 2'))); //=> false
console.log(evaluate.sync(parse('1 < 2'))); //=> true
// with context object
console.log(evaluate.sync(parse('page.title === "home"'), { page: { title: 'home' } })); //=> trueOptions
booleanLogicalOperators
Type: boolean
Default: undefined
Force logical operators to return a boolean result.
console.log(await evaluate(parse('a && b'), { a: undefined, b: true })); //=> undefined
console.log(await evaluate(parse('a && b'), { a: undefined, b: false })); //=> undefined
console.log(await evaluate(parse('a || b'), { a: false, b: null })); //=> null
console.log(await evaluate(parse('a || b'), { a: false, b: undefined })); //=> undefined
//
// With booleanLogicalOperators enabled
//
const options = {
booleanLogicalOperators: true
};
console.log(await evaluate(parse('a || b'), { a: false, b: null }, options)); //=> false
console.log(await evaluate(parse('a && b'), { a: undefined, b: true }, options)); //=> false
console.log(await evaluate(parse('a && b'), { a: undefined, b: false }, options)); //=> false
console.log(await evaluate(parse('a || b'), { a: false, b: undefined }, options)); //=> falsefunctions
Type: boolean
Default: false
Allow function calls to be evaluated. This is unsafe, please enable this option at your own risk. As an extra precaution, to evaluate functions you must also enable the generate option.
Example
See the generate docs for an example.
generate
Type: boolean
Default: undefined
Pass the .generate() function from the escodegen library to enable function evalution. For functions to be evaluated you must also set the functions option to true.
Example
const { parse } = require('esprima');
const { generate } = require('escodegen');
const { evaluate } = require('eval-estree-expression');
const options = {
functions: true,
generate
};
console.log(await evaluate(('[1, 2, 3].map(n => n * x);'), { x: 2 }, options))); // =>, [2, 4, 6]regexOperator
Type: boolean
Default: true
In expressions, if you wish to test a value using a regular expression, you have two options:
- Enable function support so that you can use methods like
.test()and.match(), or - Use this option, which enables support for a special syntax for matching against regular expressions, without the need to enable support for evaluating functions.
In other words, instead of having to do this:
console.log(evaluate.sync(parse('/^ab+c$/ig.test("abbbbbc")'), {}, { functions: true }));You can do this:
console.log(evaluate.sync(parse('name =~ /^a.*c$/'), { name: 'abc' }));
console.log(evaluate.sync(parse('name =~ regex'), { name: 'abc', regex: /^a.*c$/ }));strict
Type: boolean
Default: false
Throw an error when variables are undefined.
withMembers
Type: boolean
Default: undefined
About
Contributing
Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.
Running Tests
Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:
$ npm install && npm testBuilding docs
(This project's readme.md is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the .verb.md readme template.)
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$ npm install -g verbose/verb#dev verb-generate-readme && verbRelated projects
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Author
Jon Schlinkert
License
Copyright © 2021, Jon Schlinkert. Released under the MIT License.
This file was generated by verb-generate-readme, v0.8.0, on September 05, 2021.