Private, Public & Inheritance in JS

Access an iframe and its contents using selectors

document.getElementById('frame_id').contentWindow.$('#' + idOfElementInFrame);

Adding without using + operator

function addWithoutPlusOperator (a, b){ // 111, 111
    var sumWithoutCarry = a ^ b; // 000
    var carryWithoutSum =  (a & b) << 1;  //111 << 1 = 1110
    return addWithoutPlusOperator( sumWithoutCarry, carryWithoutSum );
}

Swapping without using extra variable

function swap (a, b){ // 5,7

    a = b - a; // 7-5 = 2

    b = b - a; // 7-2 = 5

    a = a + b; // 2 + 5 = 7

}

Private, Public variables using Javascript closures

Find Duplicate Element

Given: a list of integers where, the integers in the list are in the range 1..n and the list has a length of n+1. Find the duplicate element. The complexity of should be at most O(n).

Link to Code on JSfiddle: https://jsfiddle.net/dhiviyad/zwsan7zt/1/ 

Javascript - regular function call vs using new

function test(){
  this.a = 1;
  return a;
}

var a = test(); //a equals 1, this context in test will be window
var b = new test(); //b equals "test {a: 1}", this context is the function's context