log-instance

A minimalistic, extensible logging class that works on the browser or in NodeJS
and lets you use the same Javascript code for front- or back-end.

$3

``
npm install --save log-instance
`

$3

See test/log-instance.js

##### logInstance()
Complex systems require global and local control over logging.
Overall one might care only about warn() and error() messages,
but one might, wish to log more detail for a particular
object.

To deal with this usecase, logInstance() lets you decorate any object
and turn it into a logger with its own logLevel.

`
var aObj = {name:"A"};
logger.logLevel = 'warn'; // ignore 'info' messages
logger.logInstance(aObj); // decorate aObj with logger methods/props
aObj.logLevel = 'info'; // locally enable 'info' messages
logger.info("Shared logger ignores this message");
aObj.info("A says hello");
console.log(logger.lastLog()); // A says hello
`

##### logLevel
There are four logging levels: _debug_, _info_, _warn_ and _error_.
The logging level can be set on individual object instances or in
the shared LogInstance.singleton.

`
var logger = LogInstance.singleton;
logger.debug("nobody hears me"); // ignored by default 'info' logLevel
logger.info("hello"); // production message (normal)
logger.warn("oops"); // production message (unusual condition)
logger.error("E_DEATH", "I died"); // production message (fatal condition) throw E_DEATH
`

##### log()
A class can decorate instances with a log() method
that logs at 'info' level (i.e., "I") and automatically
includes the class name.

`
const { LogInstance } = require('log-instance');

class Koala {
constructor(opts={}) {
var logger = opts.logger || LogInstance.singleton;
logger.logInstance(this);
this.log('hello world!'); // 20200929 11:24:51 I Koala: hello world!
}
}

`

#### lastLog(level)
Returns most recently logged text for given level.

`
logger.error("goodbye world");
logger.lastLog("error"); // ... ERROR goodbye world
`

$3


#### logLevel (global/instance)
`
var myUtil = new MyUtility();
myUtil.log("hello world"); // 20200829 17:58:42 I MyUtility: hello world

logger.logLevel = "warn"; // suppress 'info' messages
myUtil.log("nobody hears me!"); // ignored
logger.info("nobody hears us!"); // ignored

myUtil.logLevel = "info"; // override logLevel for instance
myUtil.log("I hear me!"); // 20200829 17:58:42 I MyUtility: I hear me!
logger.info("we're still ignored!"); // ignored
`
#### AWS Logging
Suppress timestamp and logging level for AWS CloudWatch logs
`
require {terseLogger:logger} = require("log-instance");
logger.info("hello"); // No timestamp or logging level in output
``