Usage of call(), apply(), bind() in js

call-apply-bind.js

var person = {
  firstname: 'John',
  lastname: 'Doe',
  getFullName: function() {
    return this.firstname + ' ' + this.lastname;
  }
}

var logName = function(arg1, arg2) {
  console.log('Logged: ' + this.getFullName());
  console.log('Arguments: ' + arg1 + ' ' + arg2);
}

var logPersonName = logName.bind(person); // bind() will copy the function and invoke later
logPersonName('en');

logName.call(person, 'en', 'es');     // call() pass argument normally and invoke immediately
logName.apply(person, ['en', 'es']);  // apply() pass argument as an array and invoke immediately



/****** FUNCTION BORROWING ******/
// calling function from a scope but provide it with another 'this'
var person2 = {
  firstname: 'Foo',
  lastname: 'Bar'
}

console.log(person.getFullName.apply(person2)); // print 'Foo Bar'



/****** FUNCTION CURRYING ******/
// hardcode some arguments for a function call
function multiply(a, b) {
  return a * b;   
}

var multipleByTwo = multiply.bind(this, 2);
console.log(multipleByTwo(4));  // print '8'