CODE EXAMPLE FOR JAVASCRIPT

console log on html

(function (logger) {
    console.old = console.log;
    console.log = function () {
        var output = "", arg, i;

        for (i = 0; i < arguments.length; i++) {
            arg = arguments[i];
            output += "<span class="log-" + (typeof arg) + "">";

            if (
                typeof arg === "object" &&
                typeof JSON === "object" &&
                typeof JSON.stringify === "function"
            ) {
                output += JSON.stringify(arg);   
            } else {
                output += arg;   
            }

            output += "</span>&nbsp;";
        }

        logger.innerHTML += output + "<br>";
        console.old.apply(undefined, arguments);
    };
})(document.getElementById("logger"));

// Testing
console.log("Hi!", {a:3, b:6}, 42, true);
console.log("Multiple", "arguments", "here");
console.log(null, undefined);
console.old("Eyy, that's the old and boring one.");