Part 5- A Smarter Way to Learn JavaScript

Question 1

If you use the “indexOf()” method and it does not find your term within the text, what does it return?

Answer 1

-1

Question 2

How would you program an IF statement to test if a term is found in certain text?

Answer 2

1. assign the index number of a term to a variable, like indexNumber
2. Use the indexOf method to find the index number of the term
3. if (indexNumber !=== -1) {

Question 3

In an “indexOf()” function, the parentheses hold the term you’re searching for. What sorts of things can go in the parentheses?

Answer 3

*a string
*a variable
*a slice statement
*maybe lots of other things?

Question 4

How do you pull a single character from a string?

Answer 4

stringName.charAt(x)
where x = the index number

Question 5

What is one drawback of charAt(x)?

Answer 5

It doesn’t let you change the character. It just lets you find it.

Question 6

How do I use charAt to find the last digit of a particular string when I don’t know how long the string is?

Answer 6

varName.charAt(str1.length - 1)

Question 7

What’s the easiest way to replace part of a string with something else?

Answer 7

replace()

string.replace(“old text”, “new text”);

Question 8

The basic replace method replaces how many instances?

Answer 8

Just the first one.
To get it to replace everything, you have to put “//g” around it like this: /replace me/g

Question 9

In a replace () method, how do you keep the original version in tact?

Answer 9

Assign the change to a new variable:
y = x.replace(“a”, “b”);

but x = x.replace(“a”, “b”); will overwrite the original

Question 10

Do you have to set a replace() method to a variable, even the same variable?

Answer 10

No. These are the same for the var x
:
alert(x.replace(“up”, “on”));

alert(x= x.replace(“up”, “down”));

Question 11

What does it mean when
indexOf () returns a -1?

Answer 11

That the term was not found within that string.

Question 12

How do you round a number to the nearest whole number?

Answer 12

Math.round(numX);

Question 13

How do you round a number to the nearest whole number without losing the original number?

Answer 13

*set up a new variable

numY = Math.round(numX);

numY becomes the rounded number while the original numX is preserved.

Question 14

How do you round a number down to the nearest integer?

Answer 14

Math.floor(12.34);

Question 15

How do you round a number up to the nearest integer?

Answer 15

Math.ceil(12.34);

Question 16

What’s the code for generating a random number?

Answer 16

Math.random();

Question 17

How long is the number that Math.random() generates?

Answer 17

16 digits between zero and one.

Question 18

How would you change a number generated by Math.random() into something usable, like one of the six numbers from a die?

Answer 18

Multiply by six, then add 1.

Then round to floor.

*You have to add one because if you don’t, there is no rounding function that gets all generated digits to the numbers 1-6

Question 19

Code for converting a string to an integer? (whole number)

Answer 19

parseInt(“165”);

Question 20

Code for converting a string to a decimal number?

Answer 20

parseFloat(“165”);