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//1. call() or Function.prototype.call()
var obj = {name:"Niladri"};

var greeting = function(a,b,c){
    return "welcome "+this.name+" to "+a+" "+b+" in "+c;
};

console.log(greeting.call(obj,"Newtown","KOLKATA","WB"));
// returns output as welcome Niladri to Newtown KOLKATA in WB
//The first parameter in call() method sets the "this" value, which is the object, on which the function is invoked upon. In this case, it's the "obj" object above.
//The rest of the parameters are the arguments to the actual function.

//2. apply() or Function.prototype.apply()
var obj = {name:"Niladri"};

var greeting = function(a,b,c){
    return "welcome "+this.name+" to "+a+" "+b+" in "+c;
};

// array of arguments to the actual function
var args = ["Newtown","KOLKATA","WB"];  
console.log("Output using .apply() below ")
console.log(greeting.apply(obj,args));

/* The output will be 
  Output using .apply() below
 welcome Niladri to Newtown KOLKATA in WB */
 
//3. bind() or Function.prototype.bind()
var obj = {name:"Niladri"};

var greeting = function(a,b,c){
    return "welcome "+this.name+" to "+a+" "+b+" in "+c;
};

//creates a bound function that has same body and parameters 
var bound = greeting.bind(obj); 
console.dir(bound); ///returns a function

console.log(bound("Newtown","KOLKATA","WB")); //call the bound function
//You can use call()/apply() to invoke the function immediately. 
//bind() returns a bound function that, when executed later, will have the correct context ("this") for calling the original function. 
//So bind() can be used when the function needs to be called later in certain events when it's useful.