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javascriptlambdafunctional-programminginvocation

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!');

Solution

  • 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!');