Wrapping console.log (et al.) in your own function to modify logging behavior.
You may want a simple way to:
- Enable/disable logging with a flag, e.g.,
DEBUG = true - Prefix log messages with a common string to identify message origin, e.g.,
>>> [MyClass] Hello! - Shorter logging syntax, e.g.,
log("Hello!") - Etc.
We can acheive simple log wrappings by fiddling with the arguments object available in all JavaScript functions, and utilizing Function.prototype.apply.
For the impatient, a simple demo of these concepts can be found here.
The most basic log wrap to exactly mimic console.log behavior, e.g., to shorten logging syntax, looks like the following, which applies the arguments supplied to log when calling console.log.
var log = function(){
console.log.apply(console, arguments);
}Now you can do simple things like add a DEBUG flag to enable/disable logging:
var DEBUG=true; // Enable logging
var log = function(){
if(DEBUG){
console.log.apply(console, arguments);
}
}You may want to modify the log messages, e.g., add a prefix to all logged messages to determine where the message is coming from, e.g.,
var LOG_PREFIX = "[MyClass]"
var log = function(){
// 1. Convert args to a normal array
var args = Array.prototype.slice.call(arguments);
// 2. Prepend log prefix log string
args.unshift(LOG_PREFIX + " ");
// 3. Pass along arguments to console.log
console.log.apply(console, args);
}We must convert the arguments object to a proper array to use Array.unshift. This is because the arguments object is only an "Array-like" object, i.e., you can use subscripts, e.g., arguments[0], and get its arguments.length property, but that's about it.