Dump all console javascript outputs as string

Question

I have a problem I need to get all console.log outputs is it possible to dump all console.log outputs to a one variable? I use node.js. A little bit of context: I have an output of mocha reporter and I want to have all output to format it and send it via email

Answer 1

You can use a kind of hack where you substitute console.log with another function following a kind of decorator pattern:

var logs = ''; // logs needs to be defined for the += operator
const tmp = console.log;
console.log = function(...args){ 
    logs += arg + ' '
    tmp(...args)
}

Obviously, using a global variable is not great but you can improve from there...

Answer 2

Based on the answer of @godot:

var logs = '' // logs needs to be defined for the += operator
const tmp = console.log
console.log = function(...args) {
  // string substitution, console.log style
  const formatArg = util.format(...args)
  logs += formatArg + '\n'
  tmp(...args)
}

// To test it :

console.log('test1')
// use console.log with the "printf" style
console.log('test%d', 2)
// same
console.log('%s%d', 'test', 3)
// now show all the logs that were collected in the global var logs variable
console.log('logs: ', logs) // if you don't like globals, u can also use put it in an attribute of the console object...