expression-eval
JavaScript expression parsing and evaluation.
⚠️ UNMAINTAINED: The expression-eval npm package is no longer maintained. The package was originally published as part of a now-completed personal project, and I do not have incentives to continue maintenance. Please feel free to use the code, but be aware that support and updates will not be available.
⚠️ SECURITY NOTICE: As mentioned under Security below, this library does not attempt to provide a secure sandbox for evaluation. Evaluation involving user inputs (expressions or values) may lead to unsafe behavior. If your project requires a secure sandbox, consider alternatives such as vm2.
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Installation
Install:
npm install --save expression-eval
Import:
// ES6
import { parse, eval } from 'expression-eval';
// CommonJS
const { parse, eval } = require('expression-eval');
// UMD / standalone script
const { parse, eval } = window.expressionEval;
API
Parsing
import { parse } from 'expression-eval';
const ast = parse('1 + foo');
The result of the parse is an AST (abstract syntax tree), like:
{
"type": "BinaryExpression",
"operator": "+",
"left": {
"type": "Literal",
"value": 1,
"raw": "1"
},
"right": {
"type": "Identifier",
"name": "foo"
}
}
Evaluation
import { parse, eval } from 'expression-eval';
const ast = parse('a + b / c'); // abstract syntax tree (AST)
const value = eval(ast, {a: 2, b: 2, c: 5}); // 2.4
Alternatively, use evalAsync for asynchronous evaluation.
Compilation
import { compile } from 'expression-eval';
const fn = compile('foo.bar + 10');
fn({foo: {bar: 'baz'}}); // 'baz10'
Alternatively, use compileAsync for asynchronous compilation.
Security
Although this package does avoid the use of eval(), it cannot guarantee that user-provided expressions, or user-provided inputs to evaluation, will not modify the state or behavior of your application. This library does not attempt to provide a secure sandbox for evaluation. Evaluation of arbitrary user inputs (expressions or values) may lead to unsafe behavior. If your project requires a secure sandbox, consider alternatives such as vm2.
License
MIT License.
