Is there a way to print the console log from JavaScript, into HTML?

Question

Say I had some JavaScript function which, when run, logged its output in the console - using console.log() . After the function has run, is there a way to make it export the result into the HTML console?

Thanks

Answer 1

You can overwrite the default function with your own function.

(function () {

    // save the original console.log function
    var old_logger = console.log;

    // grab html element for adding console.log output
    var html_logger = document.getElementById('html_logger');

    // replace console.log function with our own function
    console.log = function(msg) {

      // first call old logger for console output
      old_logger.call(this, arguments);

      // check what we need to output (object or text) and add it to the html element.
      if (typeof msg == 'object') {
        html_logger.innerHTML += (JSON && JSON.stringify ? JSON.stringify(msg) : msg) + '<br>';
      } else {
        html_logger.innerHTML += msg + '<br>';
      }
    }
})();

Here is a JSFiddle to complete the answer with a working example.

http://jsfiddle.net/djr0mj9p/1/

Answer 2

You can extend console.log function:

function extendLog(logger) {
    var original = console.log;
    console.log = function() {
        logger(Array.prototype.slice.call(arguments));
        return original.apply(this, arguments);
    }
}

// custom logger
// args - array of arguments passed to console.log
var myLogger = function(args) {
    var log = document.createElement("div");
    log.innerHTML = args;
    document.body.appendChild(log);
}

extendLog(myLogger);

console.log("Hello world!");
console.log("How", "are", "you?");

extendLog function has one argument which is your logging function. You can also call extendLog multiple times with different loggers.