https://github.com/rustwasm/console_error_panic_hook

A panic hook for wasm32-unknown-unknown that logs panics with console.error
https://github.com/rustwasm/console_error_panic_hook

console panic-hook rust rust-wasm wasm

Last synced: 4 days ago
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A panic hook for wasm32-unknown-unknown that logs panics with console.error

• Host: GitHub
• URL: https://github.com/rustwasm/console_error_panic_hook
• Owner: rustwasm
• License: apache-2.0
• Created: 2018-05-23T22:25:27.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2022-12-04T18:10:44.000Z (almost 2 years ago)
• Last Synced: 2024-11-08T16:09:59.880Z (4 days ago)
• Topics: console, panic-hook, rust, rust-wasm, wasm
• Language: Rust
• Size: 504 KB
• Stars: 326
• Watchers: 5
• Forks: 24
• Open Issues: 12
• Metadata Files:
  • Readme: README.md
  • License: LICENSE-APACHE

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README

        
## `console_error_panic_hook`

[![](https://docs.rs/console_error_panic_hook/badge.svg)](https://docs.rs/console_error_panic_hook/)

[![](https://img.shields.io/crates/v/console_error_panic_hook.svg)](https://crates.io/crates/console_error_panic_hook)

[![](https://img.shields.io/crates/d/console_error_panic_hook.png)](https://crates.io/crates/console_error_panic_hook)

[![Build Status](https://travis-ci.org/rustwasm/console_error_panic_hook.svg?branch=master)](https://travis-ci.org/rustwasm/console_error_panic_hook)

This crate lets you debug panics on `wasm32-unknown-unknown` by providing a

panic hook that forwards panic messages to

[`console.error`](https://developer.mozilla.org/en-US/docs/Web/API/Console/error).

When an error is reported with `console.error`, browser devtools and node.js

will typically capture a stack trace and display it with the logged error

message.

Without `console_error_panic_hook` you just get something like *RuntimeError: Unreachable executed*

Browser:

![Console without panic hook](without_panic_hook.png)

Node:

![Node console without panic hook](without_panic_hook_node.png)

With this panic hook installed you will see the panic message

Browser:

![Console with panic hook set up](with_panic_hook.png)

Node:

![Node console with panic hook set up](with_panic_hook_node.png)

### Usage

There are two ways to install this panic hook.

First, you can set the hook yourself by calling `std::panic::set_hook` in

some initialization function:

```rust

extern crate console_error_panic_hook;

use std::panic;

fn my_init_function() {

    panic::set_hook(Box::new(console_error_panic_hook::hook));

    // ...

}

```

Alternatively, use `set_once` on some common code path to ensure that

`set_hook` is called, but only the one time. Under the hood, this uses

`std::sync::Once`.

```rust

extern crate console_error_panic_hook;

struct MyBigThing;

impl MyBigThing {

    pub fn new() -> MyBigThing {

        console_error_panic_hook::set_once();

        MyBigThing

    }

}

```

### Error.stackTraceLimit

Many browsers only capture the top 10 frames of a stack trace. In rust programs this is less likely to be enough. To see more frames, you can set the non-standard value `Error.stackTraceLimit`. For more information see the [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Microsoft_Extensions/Error.stackTraceLimit) or [v8 docs](https://v8.dev/docs/stack-trace-api).