solc-js

1.0.1 verified Fri May 01 auth: no javascript

solc-js v1.0.1 is a cross-browser JavaScript bindings for the Solidity compiler, using Emscripten-compiled solc binaries from the solc-bin repository. It is designed as a smaller and faster alternative to the solc package for browser-only environments, while solc or solc-native are recommended for Node.js. It provides an async API to fetch compiler versions, compile Solidity source code, and resolve imports. It has a moderate release cadence and is maintained as part of the ethereum-play project on GitHub.

Common errors

error require is not defined in ES module scope ↓

cause Trying to use CommonJS require with solc-js, which is ESM-only in v1.0+.

fix

Switch to ESM imports: import solcjs from 'solc-js';

error TypeError: solcjs is not a function ↓

cause Using `require('solc-js')` without .default (CommonJS interop) with older bundlers.

fix

Use const solcjs = require('solc-js').default; or upgrade to ESM.

error Uncaught TypeError: compiler is not a function ↓

cause Calling `await solcjs(version)` and then calling `compiler(source)` on the result, but `solcjs` itself is the compiler (no need to call twice).

fix

Use const compiler = await solcjs(version); const output = await compiler(source); correctly.

Warnings

breaking solc-js v1.0.0+ is ESM-only, breaking CommonJS require. ↓

fix Use ESM imports (`import solcjs from 'solc-js'`) or dynamic import in Node.js.

deprecated The default export `solcjs(version)` now returns a compiler function, not a compiler object with `.version`. ↓

fix Access `.version` from the `solcjs` module itself: `const { version } = await solcjs(version);` is incorrect; use `const compiler = await solcjs(version);` and check compiler.version if needed.

gotcha When calling `solcjs()` without version, it fetches the latest release, which may be a nightly build. ↓

fix Always specify a version string to avoid unexpected compiler versions. Use `versions().releases[0]` for stable.

gotcha Using `solcjs` in Node.js is not recommended; it may be slower and have different behavior than the native `solc` package. ↓

fix For Node.js, use `solc` or `solc-native` instead.

Install

npm install solc-js

yarn add solc-js

pnpm add solc-js

Imports

default
wrong
```
const solcjs = require('solc-js')
```
correct
```
import solcjs from 'solc-js'
```
solc-js is ESM-only; CommonJS require will fail. Use dynamic import in Node.js if needed.
types
wrong
```
None
```
correct
```
import type { SolcJS, CompilerOutput } from 'solc-js'
```
TypeScript types are exported but minimal; consider declaring own types for compiler output.

versions

wrong

const { versions } = require('solc-js')

correct

const { versions } = await import('solc-js')

CommonJS require does not work; use dynamic import or ESM.

version2url

wrong

const version2url = solcjs.version2url

correct

const { version2url } = await import('solc-js')

Named export, not a method on the default export.

Quickstart

Import solc-js, fetch available versions, load a specific compiler, and compile a simple Solidity contract.

import solcjs, { versions } from 'solc-js';

async function compile() {
  const allVersions = await versions();
  console.log('Available releases:', allVersions.releases);
  const version = allVersions.releases[0] || 'v0.8.20-stable-2023.06.13';
  const compiler = await solcjs(version);
  const source = `
    pragma solidity ^0.8.0;
    contract HelloWorld {
      string public greeting = "Hello, World!";
    }
  `;
  const output = await compiler(source);
  console.log('Compiled bytecode:', output.bytecode);
}
compile().catch(console.error);