Homework for Week 1:

Ex 2.1 :((4 >= 6) || ("grass" != "green")) && !(((12 * 2) == 144) && true)

Is this true?

Solution: There are two expressions connected by &&.

The first part ((4>=6)||("grass"!="green")).

4>=6 is false.But grass!=green is true. So, this expression

is true.

The second part (((12*2)==144) && true).

(12*2)==144 is true. trues itself is always truthy.So, this

expression is true. (true && true)

So, true && true gives true.

Ex 2.2: Use the techniques shown so far to write a program that calculates and shows the value of 210 (2 to the 10th power). You are, obviously, not allowed to use a cheap trick like just writing 2 * 2 * ....

Solution: Since, upto this point, only the while loop is explained, I am going to use this:

var result=1;

var counter=1;

while(counter<=10)

{ result=result*2;

counter=counter+1;

}

print(result);

Ex 2.3: With some slight modifications, the solution to the previous exercise can be made to draw a triangle. And when I say 'draw a triangle' I mean 'print out some text that almost looks like a triangle when you squint'.

Print out ten lines. On the first line there is one '#' character. On the second there are two. And so on.

Solution: Here, again I will use the while loop:

var line=" ";

var counter=1;

while(counter<=10)

{ line=line+"#"; // concatenating the hashes

counter=counter+1;

print(line);

}

Ex 2.4: Rewrite the solutions of the previous two exercises to use for instead of while.

Solution: first problem-

var result=1;

var i=1;

for(i=1;i<=10;i++)

result=result*2;

print(result);

second problem:

var line=" ";

var i=1;

for(i=1;i<=10;i++)

{ line=line+"#";

print(line);

}

Ex 2.5:Write a program to ask yourself, using prompt, what the value of 2 + 2 is. If the answer is "4", use alert to say something praising. If it is "3" or "5", say "Almost!". In other cases, say something mean.

Solution: var ans=prompt("what is 2+2?","think!!!");

if(ans=="4")

alert("Bravo!!");

else if((ans=="3")||(ans="5"))

alert("Almost!");

else

alert("Stupid!!");

Ex 2.6:Add a while and optionally a break to your solution for the previous exercise, so that it keeps repeating the question until a correct answer is given.

Solution:

var ans;

while(ans!=4)

{

var ans=prompt("what is 2+2?","think!!!");

if(ans=="4")

{alert("Bravo!!");

break;}

else if((ans=="3")||(ans="5"))

alert("Almost!");

else

alert("Stupid!!");

}

Note: In the above solution, the break statement is really unnecessary.

Final Question: Create an example that shows a valid use of the 'guard' and 'default' operators in Javascript

Solution:

The && operator is also called the guard or the logical and operator. The && operator returns the first operand only if it is falsy(i.e, false,null,undefined,"",0) .Otherwise, it returns the second operand .

eg: var ans=prompt("Predict a number","");

var b=10;

var value= ((ans==10) && "Correct prediction!!!");

In the above example, the user is asked to predict a number. If the answer matches 10, then the output "Correct prediction!!!" is to be stored in a variable and displayed on the screen.

The || operator is also called the 'default' or the logical or operator. The || operator returns the second operand only if the first is falsy(i.e, false,null,undefined,"",0) .

eg: var ans=prompt("Predict a number","");

var b=10;

var value=((ans!=10) || "Wrong prediction.")

The above example is just the opposite of the previous example. Here if the user doesn't enter 10, wrong prediction is stored.