1. JavaScript Strings and Arrays
Kevin Harville

2. Strings and Arrays Strings are indexed groups of CHARACTERS.
Arrays are indexed groups of numbers.
Therefore we can refer to a particular number or letter by referring to its index.

3. Array Examples I could have an array of images:
myImage[1] = “myDog.jpg”
myImage[2] = “myCat.jpg”
myImage[3] = “myFish.jpg”
Or an array of the students’ scores:
classScore[0] = 100
classScore[1] = 95
classScore[2] = 86

4. Strings and Arrays
Strings and Arrays are objects rather than variables.
Objects have properties and methods
myString = “Kevin” makes it look like a variable, but is actually a shortcut to make strings easy to use.
IMPORTANT: Strings and Arrays are indexed, or counted, starting at 0, not 1.

5. String Properties
myString.length

6. String Methods String objects have several useful methods:
myString.toLowerCase();
myString.toUpperCase();
Others Follow…

7. String Methods: Substring
myString.substring(start, end+1);
“Kevin”.substring(0,2) returns “Ke”
“Kevin”.substring(1,3) returns “ev”
REMEMBER: ARRAYS START AT ZERO!

8. String Methods: charAt
charAt returns the value of the character at an index position:
“Kevin”.charAt(4) returns “n” why “n”?

9. String Methods: indexOf
“Kevin”.indexOf(“vi”) returns 2
indexOf returns –1 if it is not found: Kevin.indexOf(“Joe”) returns –1
You can specify the starting position: “Rin Tin Tin”. indexOf(“in”, 4) returns 5
To find multiple occurrences repeat the process.

10. String Methods: lastIndexOf
Same as indexOf, but starts searching from the end.

11. String Methods: Split
This method creates an array myNewStrings = “Quick Brown Fox”.Split(“ “);
myNewStrings[0] = “Quick” myNewStrings[1] = “Brown” myNewStrings[2] = “Fox”

12. Some Other String Methods:
.replace (4.0 Browsers or higher)
HTML functionality, such as
.fontcolor
.fontsize
.strike
.etc.

13. Arrays Again, an array is a group of indexed values.
For instance, instead of having individual class scores Score1, Score2, etc, you can have score[0], score[1]…score[30].
So, What’s the difference?

14. Arrays
The difference is that the indexes can themselves be referred to by a variable!
score[x] = 7
score[x + 1] = 4
score[y]= 9

15. Arrays
When we want a group of related data, we may declare an Array object:
myArray = new Array(50)
This would set up 50 elements, from 0 to 49. There is no 50th element.

16. Arrays
That indexing ability makes keeping track of related data very easy.
Name[7] = “Fred”
Lab1[7] = 5
Lab2[7] = 4
Midterm[7] = 12

17. Array Object: Sort Method
Using the sort method, you can sort a numeric or alphabetic array.
MyArray.sort()

18. Summary Strings and arrays are used in most scripts
Learning them is necessary and a useful programming skill.