Add timestamp or tamper with console.log any way you want, including format string specifiers ("%s", "%d" etc.) support

chrome.console.log.js

console.logCopy = console.log.bind(console);

console.log = function()
{
    // Timestamp to prepend
    var timestamp = new Date().toJSON();
    
    if (arguments.length)
    {
        // True array copy so we can call .splice()
        var args = Array.prototype.slice.call(arguments, 0);
        
        // If there is a format string then... it must
        // be a string
        if (typeof arguments[0] === "string")
        {
            // Prepend timestamp to the (possibly format) string
            args[0] = "%o: " + arguments[0];
           
            // Insert the timestamp where it has to be
            args.splice(1, 0, timestamp);
            
            // Log the whole array
            this.logCopy.apply(this, args);
        }
        else
        { 
            // "Normal" log
            this.logCopy(timestamp, args);
        }
    }
};