[Proxyman] console.log() for JavascriptCore

If you’re using Proxyman, you might notice that the Scripting tool, which allows developers to write Javascript Code to easily manipulate Request/Response data.

This feature is powered by JavascriptCore framework from Apple.

The following list will write down what the Scripting can do:


It’s essential to provide a function that the developer can debug their code. However, console.log() is not available in the JavascriptCore framework.

Fortunately, JavascriptCore allows us to extend a new function that can mimic the basic logic of console.log().

The following snippet code would demonstrate how to do it.

// 1. Initialize context
let context = JSContext()

// 2. Register `_console.log` function that we can capture the log
// Handy tool, so the user can use their existing JS code
let consoleLog: @convention(block) (String) -> Void = {[weak script] message in
context.setObject(consoleLog, forKeyedSubscript: "_consoleLog" as NSString)

// 3. Provide a JS Wrapper
let consoleLogFunc = """
function isObject(val) {
  if (val === null) { return false;}
  return ( (typeof val === 'function') || (typeof val === 'object') );

var console = { log: function(message) {
  if (isObject(message)) {
    _consoleLog(JSON.stringify(message, null, '\t'));
  } else {

// 4. done

Then, we can use it as usual.

const myObject = { name: "Proxyman" };