Accessing line number in V8 JavaScript (Chrome & Node.js)

javascript node.js google-chrome v8
james_womack picture james_womack · Jul 8, 2012 · Viewed 27.5k times · Source

JavaScript developers who have spent time in languages like C often miss the ability to use certain types of introspection, like logging line numbers, and what method the current method was invoked from. Well if you're using V8 (Chrome, Node.js) you can employ the following.

Answer

james_womack picture james_womack · Jul 8, 2012 
Object.defineProperty(global, '__stack', {
  get: function(){
    var orig = Error.prepareStackTrace;
    Error.prepareStackTrace = function(_, stack){ return stack; };
    var err = new Error;
    Error.captureStackTrace(err, arguments.callee);
    var stack = err.stack;
    Error.prepareStackTrace = orig;
    return stack;
  }
});

Object.defineProperty(global, '__line', {
  get: function(){
    return __stack[1].getLineNumber();
  }
});

console.log(__line);

The above will log 19.

Combined with arguments.callee.caller you can get closer to the type of useful logging you get in C via macros.

Related questions

Origin <origin> is not allowed by Access-Control-Allow-Origin

XMLHttpRequest cannot load http://localhost:8080/api/test. Origin http://localhost:3000 is not allowed by Access-Control-Allow-Origin. I read about cross domain ajax requests, and understand the underlying security issue. In my case, 2 servers are running locally, and like to enable cross …

Read More
require is not defined? Node.js

Just started working with Node.js. In my app/js file, I am doing something like this: app.js var http = require('http'); http.createServer(function (request, response) { response.writeHead(200, {'Content-Type': 'text/plain'}); response.end('Am I really running a …

Read More
Copying an array of objects into another array in javascript (Deep Copy)

Copying an array of objects into another array in javascript using slice(0) and concat() doesnt work. I have tried the following to test if i get the expected behaviour of deep copy using this. But the original array is also …

Read More