iamcodemaker / console_log

A rust logger that routes messages to the browser's console.

console_log

A logger that routes messages to the browser's console.

Usage

use log::Level;
fn main() {
    console_log::init_with_level(Level::Debug);

    info!("It works!");

    // ...
}

Details

Rust's log levels map to the browser's console log in the following way.

Rust	Web Console
trace!()	console.debug()
debug!()	console.log()
info!()	console.info()
warn!()	console.warn()
error!()	console.error()

Colors

The "color" feature adds styling to the log messages.

Cargo.toml

console_log = { version = "1", features = ["color"] }

The styled log messages will be rendered as follows:

Code Size

Twiggy reports this library adding about 180Kb to the size of a minimal wasm binary in a debug build. If you want to avoid this, mark the library as optional and conditionally initialize it in your code for non-release builds.

Cargo.toml

[dependencies]
cfg-if = "0.1"
log = "0.4"
console_log = { version = "1", optional = true }

[features]
default = ["console_log"]

lib.rs

use wasm_bindgen::prelude::*;
use cfg_if::cfg_if;

cfg_if! {
    if #[cfg(feature = "console_log")] {
        fn init_log() {
            use log::Level;
            console_log::init_with_level(Level::Trace).expect("error initializing log");
        }
    } else {
        fn init_log() {}
    }
}

#[wasm_bindgen]
pub fn main() {
    init_log();
    // ...
}

Limitations

The file and line number information associated with the log messages reports locations from the shims generated by wasm-bindgen, not the location of the logger call.

License

This project is licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contributing

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

See Also

• wasm-logger
• wasm-bindgen-console-logger
• fern (use with console_log::log)

console_log's Issues

wasm-logger

Hey, this seems to provide exactly the same functionality as https://crates.io/crates/wasm-logger.

Did you not know about that crate or is there something that's handled differently in console_log?

I always try to advocate for lack of duplication where possible.

0.1.2 isn't pushed to the repository

It's on crates.io, but not pushed to master.

Configure level for specific crate

I wanna to know if it's possible to init the logger with specific level for a crate ?

Something like: https://docs.rs/env_logger/0.10.0/env_logger/struct.Builder.html#method.filter_module

Thank you very much.
Marc-Antoine

[Feature Request]: Log Filters

The logger should contain support for filters much like how pretty_env_logger can filter with the RUST_LOG environment variable or how android_logger has a with_filter method

log.trace() not working in google chrome

log.trace() not working in googlo chrome :(

Why map trace! to console.debug but not console.trace?

Would like to add this crate to "Crates You Should Know" section of rust+wasm book...

Are you OK with that?

Also, it would be good to set up dependabot for this repo to stay on top of web-sys updates.

Interested in hearing back,

Nick

Why map trace! to console.debug but not console.trace?

Contain code that will be rejected by future version of Rust

I get

warning: the following packages contain code that will be rejected by a future version of Rust: console_log v0.2.0

When compiling my project https://github.com/erwanvivien/gifski on branch wasm32 using

RUSTFLAGS="-C target-feature=+atomics,+bulk-memory,+mutable-globals" cargo build --target=wasm32-unknown-unknown --release -Z build-std=panic_abort,std

I don't know if it's normal?