What is the difference between assigning a function via “this” vs. “prototype”? [duplicate]

Answer 1

Functions assigned to the prototype will be shared by all instances; functions assigned in the constructor will have a separate function object per instance.

Also, functions assign in the constructor can use the constructor's variables and parameters.

For example:

var foo = function(param){
    this.bar = function() { alert('I can see a parameter: ' + param); };
}

foo.prototype.baz = function() { alert('I can't see foo's parameters'); };

var car = new foo("Hi there!");
car.bar();