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Uncaught TypeError: Illegal invocation in javascript

I'm creating a lambda function that executes a second function with a concrete params. This code works in Firefox but not in Chrome, its inspector shows a weird error, Uncaught TypeError: Illegal invocation. What's wrong with my code?

var make = function(callback,params){
    callback(params);
}

make(console.log,'it will be accepted!');
like image 328
fcortes Avatar asked Jan 18 '12 03:01

fcortes


2 Answers

The console's log function expects this to refer to the console (internally). Consider this code which replicates your problem:

var x = {};
x.func = function(){
    if(this !== x){
        throw new TypeError('Illegal invocation');
    }
    console.log('Hi!');
};
// Works!
x.func();

var y = x.func;

// Throws error
y();

Here is a (silly) example that will work, since it binds this to console in your make function:

var make = function(callback,params){
    callback.call(console, params);
}

make(console.log,'it will be accepted!');

This will also work

var make = function(callback,params){
    callback(params);
}

make(console.log.bind(console),'it will be accepted!');
like image 162
Paul Avatar answered Nov 01 '22 18:11

Paul


You can wrap the function which need 'this' to a new lambda function, and then use it for your callback function.

function make(callback, params) {
  callback(params);
}

make(function(str){ console.log(str); }, 'it will be accepted!');
like image 36
ifreedom Avatar answered Nov 01 '22 17:11

ifreedom