JavaScript

Question 1

Which command syntax available in Php isn’t supported by Javascript ?

Answer 1

(single line command) is not supported by JavaScript

Question 2

How to define a variable ? How is it different from Php ??

Answer 2

var variableName;

In PHP, variable name starts with $.

Question 3

Create an array and point out the difference with PHP array ?

Answer 3

var myVariable = [1, “Bob”,”Stev”,10 ]; 
var names= new Array("Tony", "Mike", "Dan");
// load array by putting values in round brackets
alert("Second element of array is: "+names[1]);
// index 1 will get 2nd element in array

In PHP, $fruits = array(“Apple”, “Grapes”);

Question 4

String concatenation

Answer 4

x= “The answer is “ + 42 //The answer is 42

In PHP, “The answer is “. 42

Question 5

querySelector()

Answer 5

Returns the first match of the <h1> tag and stores result in a Variable</h1>

Question 6

querySelectorAll()

Answer 6

Returns all matches of the <h1> tags and stores result in myVariable </h1>

Question 7

getElementsByTagName()

Answer 7

document.getElementsByTagName(‘p’);

Will get all the <p> tags in the HTML page </p>

Question 8

getElementById()

Answer 8

document.getElementById(custName)

Locates the element whose ID name is custName

Question 9

parseInt()

Answer 9

• Parses a string argument
• Extracts integer from start of string
• Ignores leading whitespaces

Question 10

parstInt() and radix examples

Answer 10

parseInt(“F”, 16); // treats it as base 16 and returns 15
parseInt(“1111”, 2); // treats it as base 2 and returns 15
parseInt(“546”, 2); // returns NaN as digits of string are not valid for binary

Question 11

parseFloat()

Answer 11

similar to parseInt, but returns a floating point number

Question 12

Number()

Answer 12

converts numeric strings to numbers – integer or float. Ignores leading whitespaces
Number(“12”);// returns 12
Number(“12.3”);// returns 12.3
Number(“12px”);// returns NaN due to present of non
-numeric values in the string

Question 13

Math.max()

Math.min()

Answer 13

Returns the largest of a given set of numbers

Returns the smallest of a given set of numbers

Question 14

Math.round()

Answer 14

Returns the value of a number, rounded to the nearest integer
Math.round( 20.49); // returns 20
Math.round(20.5); // returns 21

Question 15

alert vs prompt

Answer 15

alert is just to display the msg
prompt is two-way ie. to give msg and get answer from user
var num1=prompt(“enter first num “);
var num2=prompt(“enter second num”);
var ans=num1*num2;
alert(“The answer on multiplying your numbers is “+ans);

Question 16

How to add an element to an array ?

Answer 16

names[3]=”Tina”;

We just added another a 4th element to the end of array

Question 17

find the length of the string in JavaScript ? Is it variable.length or strlength(variable) ?

Answer 17

variable.length;

Question 18

toUpperCase() and toLowerCase()

Answer 18

string is converted to upper/lower case

Question 19

sub string = starts on 1st, end on 4th, not including 4th is

Answer 19

myCountry.substring(0,3)

Question 20

how to sort and reverse the sort, of the elements in an array ?

Answer 20

array. sort(); //to sort

array. reverse(); //to reverse