Crate console_log
source ·Expand description
A logger that logs to the browser’s console.
Example
use log::Level;
use log::info;
fn main() {
console_log::init_with_level(Level::Debug);
info!("It works!");
// ...
}
Log Levels
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() |
Getting Fancy
The feature set provided by this crate is intentionally very basic. If you need more flexible
formatting of log messages (timestamps, file and line info, etc.) this crate can be used with
the fern
logger via the console_log::log
function.
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 = "0.1", 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.
Functions
max_log_level
set to Level::Info
(a sensible default).max_log_level
to the given value.log::Record
to the browser’s console at the appropriate level.