eval5

library1.4.8jsnpmunverified

eval5 is a JavaScript interpreter written in TypeScript, designed to execute full ES5 syntax within various JavaScript environments including browsers, Node.js, and mini-programs like WeChat and Taro. Currently at version 1.4.8, the project maintains an active release cadence, primarily focusing on bug fixes and minor improvements. Its key differentiators include providing a sandboxed execution environment, allowing control over script execution time, and enabling JavaScript execution in environments where native `eval` or `Function` constructors are unavailable or restricted. It's particularly useful for scenarios requiring isolated script execution or educational purposes, strictly adhering to the ES5 specification without support for newer ECMAScript features.

web-framework

npm install eval5

github ↗package ↗

INSTALL

IMPORT

SIG · EVAL5

eval5

web-frameworkjavascriptv1.4.8

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

Interpreter

✓ import { Interpreter } from 'eval5'

✗ const Interpreter = require('eval5').Interpreter

This is the primary class for creating an interpreter with a persistent context. Use for scenarios requiring stateful execution across multiple calls.

evaluate

✓ import { evaluate } from 'eval5'

✗ const evaluate = require('eval5').evaluate

A utility function for one-off code execution. It creates a new Interpreter instance for each call, meaning no state is shared between invocations.

Function

✓ import { Function } from 'eval5'

✗ const CustomFunction = require('eval5').Function

This is `eval5`'s wrapped `Function` constructor, distinct from the native JavaScript `Function`. It creates functions within the interpreter's context, respecting its scope and `globalContextInFunction` settings.

Demonstrates how to create an `Interpreter` instance with a custom global context and options, then execute multiple JavaScript code snippets sequentially, maintaining state across calls and logging results.

import { Interpreter } from "eval5"; // Define a custom context for the interpreter const myContext = { customVar: 42, log: (...args: any[]) => console.log('INTERPRETER LOG:', ...args) }; const interpreter = new Interpreter(myContext, { timeout: 5000, // Set a timeout for execution (5 seconds) // globalContextInFunction: window // For browser environments to set 'this' in functions }); let result; try { interpreter.evaluate("var a = 100;"); interpreter.evaluate("var b = customVar * 2;"); result = interpreter.evaluate("a + b;"); myContext.log(`First evaluation result: ${result}`); // INTERPRETER LOG: First evaluation result: 184 interpreter.evaluate("function add(x, y) { return x + y; }"); result = interpreter.evaluate("add(a, b);"); myContext.log(`Second evaluation result (calling function): ${result}`); // INTERPRETER LOG: Second evaluation result (calling function): 184 // Demonstrate scope isolation const outerScopeVar = 500; interpreter.evaluate(` var c = ${outerScopeVar}; log('Inside interpreter, c is:', c); var d = 10; `); // Accessing 'd' outside the interpreter's scope would fail: // console.log(interpreter.evaluate("d;")); // ReferenceError: d is not defined myContext.log('Interpreter operations complete.'); } catch (e: any) { console.error("Interpreter error:", e.message); }

Debug

Known issues

breakingThe `rootContext` property on the `Interpreter` constructor options was removed in version 1.4.0. It was replaced by `globalContextInFunction`.

fix

Use `globalContextInFunction` option in the `Interpreter` constructor instead of `rootContext` to control the 'this' context within functions.

affects: >=1.4.0

gotchaBy default, `this` inside functions evaluated by `eval5` will be `undefined`, unlike native non-strict JavaScript where it defaults to the global object. This can lead to unexpected behavior for code expecting `this` to point to `window` or `global`.

fix

Set the `globalContextInFunction` option in the `Interpreter` constructor or globally via `Interpreter.globalContextInFunction` to the desired global object (e.g., `window` or `globalThis`) to control `this` behavior in functions.

affects: All

gotchaWhen calling host environment methods (like `alert` or `console.log`) passed into the interpreter's context, you might encounter 'Illegal invocation' errors if the methods are not correctly bound. This happens because `eval5` might call them without the correct `this` context.

fix

Bind host functions explicitly when passing them to the interpreter's context. For example: `const ctx = { alert: alert.bind(window) };` or `const ctx = { console: { log: console.log.bind(console) } };`.

affects: All

gotchaeval5 only supports the ES5 specification. It does not parse or execute newer ECMAScript features (ES6+), such as `let`/`const`, arrow functions, classes, modules, or async/await.

fix

Ensure that all JavaScript code provided to `eval5` is transpiled down to ES5 syntax using tools like Babel if it originates from a newer ECMAScript version.

affects: All

Errors

Common errors & fixes

ReferenceError: <variable_name> is not defined

Attempting to access a variable that was defined in a previous `evaluate` call using the standalone `evaluate` function, or accessing a variable not in the current interpreter's scope.

fix

If you need shared state across multiple code snippets, use an `Interpreter` instance. If using the standalone `evaluate` function, pass all necessary variables and functions into its `ctx` parameter for each invocation.

TypeError: Illegal invocation

A host environment function (like `alert` or `console.log`) was called from within the `eval5` interpreter without its original `this` context.

fix

Bind the host function to its original object before passing it into the interpreter's context. Example: `new Interpreter({ alert: window.alert.bind(window) })`.

TypeError: Cannot read properties of undefined (reading '<property>')

Attempting to access a property on `this` inside a function executed by `eval5` when `this` is `undefined` (which is the default behavior if `globalContextInFunction` is not set).

fix

Configure the `globalContextInFunction` option in the `Interpreter` constructor or globally via `Interpreter.globalContextInFunction` to set the desired `this` context for functions.

Upgrade

Version history

1.4.8latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

8 hits · last 30 days

node

Resources

githubhttps://github.com/bplok20010/eval5 ↗

packagehttps://www.npmjs.com/package/eval5 ↗