How to Alter console.log

Introduction

If you need to alter Node.JS server or JavaScript client console.log function w/o the vsprintf library, dynamically build the util.format command and execute with JavaScript eval().

Using the Code

Place the following code in your file to replace the default console.log function:

util = require('util');
console.log = function(a) {
    if (arguments.length>1) {
        var cmd = 'util.format(';
        for (i in arguments) {
            if (i>0)
                cmd += ',';
            cmd += 'arguments['+i+']';
        }
        cmd += ')';
        util.log(eval(cmd));
    }
    else
        util.log(a);
};

This is much better:

util = require('util');
console.log = function() {
    process.stdout.write((new Date()).toISOString().substring(0,19).replace('T', ' ')+': ');
    process.stdout.write(util.format.apply(this, arguments) + '\n');
};

History

• September 15, 2013 - First version.
• October 31, 2013 - Found a better way to do the same thing.