Sep 12, 2014

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JavaScript Quiz-1

1. What is outcome of  x == y ? 
var x = "ZYTHAM";             
var y = new String("ZYTHAM");
x==y //prints true/false
Answer: true
== compares values of x and y . Since x and y both has equal values.

2. What will outcome of x === y ?
var x = "ZYTHAM";             
var y = new String("ZYTHAM");
x===y
Answer: false
=== compares both values and type. x is of type String and y is of type Object, It can be verified executing :
typeof x  "string"
typeof  y  "object"

3. What will be outcome of x == y and x === y ?
var x = new String("ZYTHAM");             
var y = new String("ZYTHAM");
x==y //prints true/false
x===y //prints true/false
Answer:  Both prints false.
== prints false because both object are different object. And similarly, === prints false because both are different object.

4. What will be outcome of res and res1 ?
var str = "Nikhil, Ranjan, Devinline";
var res = str.substr(8, 6);
var res1 = str.slice(-17, -11);
Answer: Both will display "Ranjan"
substr(8,6) - starts from index 8 and prints length of 6 char. (start index is 0)
substr(-17,-11) - starts from end(go back 17 chars and then then reaches 11 from end)

5. What will be outcome of below sample unit
var myNumber = 64;
myNumber.toString(16);     
myNumber.toString(8);      
myNumber.toString(2);   
Answer:
myNumber.toString(16);
"40"
myNumber.toString(8);
"100"
myNumber.toString(2);
"1000000"

6. Write a random number generator function in javascript, provided random number should be generated between min and max passed as input.
Answer:
min is included and max is excluded
function getRndomInteger(min, max) {
    return Math.floor(Math.random() * (max - min) ) + min;
}

min and max both are included
function getRndomInteger(min, max) {
    return Math.floor(Math.random() * (max - min + 1) ) + min;
}

7. Predict outcome of sample code ?

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.sort();  
var points = [40, 100, 1, 5, 25, 10];
points.sort();
Answer:-
["Apple", "Banana", "Mango", "Orange"]
[1, 10, 100, 25, 40, 5]

First output looks as expected, but what happened to second array output. By default, the sort() function sorts values as strings. So, "25" is bigger than "100", because "2" is bigger than "1".

8. Sort above array(number array) in ascending order ? Hint: Use compare function in sort function

var points = [40, 100, 1, 5, 25, 10];
function comparefun(a, b){
  return a - b
}
points.sort(comparefun);
On passing a compare function to sort method, sort method sort numbers as follows.
 [1, 5, 10, 25, 40, 100]
Note:- The purpose of the compare function is to define an alternative sort order(instead of natural sort ordering).The compare function should return a negative, zero, or positive value, depending on the arguments:

9. Sorting Object Arrays based on some attributes - Below arrays contains objects. Sort below objects based on salary.
var positions = [
{type:"VP", Salary:80},
{type:"Manager", Salary:40},
{type:"Director", Salary:50}];
Answer:-  positions.sort(function(a, b){return a.Salary - b.Salary});
Above code lines sort positions array of objects in ascending order, same can be validated with following console output

10. Write a compare function to sort array based on type and verify the output.
Answer:
positions.sort(function(a, b){
    var x = a.type.toLowerCase();
    var y = b.type.toLowerCase();
    if (x < y) {return -1;}
    if (x > y) {return 1;}
    return 0;
});

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