OBJECTIVE

• Define and use functions.  

DISCUSSION

Functions 

• A set of statements that performs a task. 
• Define once, use many times
• Can pass parameters into a function
• Can return a value
• Example:

DEFINING THE FUNCTION...

function addNums(fX,fY) { 

    var fSum

    fSum = fX + fY 

    return(fSum)

    /*could replace these 3 lines with

      return(fX + fY) */

    }

DEFINING AND CALLING A FUNCTION...

function displaySum(fXX, fYY) {

    var fTotal

    fTotal = addNums(fXX, fYY)

    alert(fTotal)

    /* Could replace these 3 lines with

    alert(addNums(fXX, fYY)  */

    }

CALLING THE FUNCTION FROM HTML...

 

<div id = "myID" onclick = "alert(addNums(3,5)">Click to add 3 and 5</div>
</body>
  

EXERCISES

1.  Write a function that accepts three numbers and returns their sum.

2.  Write a function that accepts three numbers and returns their average. Use the function from #1. Create a page to test your function.  Add three textboxes and a button.  When the user clicks the button, the contents the average of the textboxes should be displayed.

3.  Write a function that accepts two strings, adds them together (with a space between them), and returns the combined string.  Create a page to test your function.

4.  Write a function that accepts two textboxes as objects and switches their values.

5.  Write a function that accepts an object and two values representing the distance in the horizontal and vertical directions. The object should be moved the amount specified.

LINKS AND HELP