Getting Started

Let’s take the addition or sum example, which is common to all methods regardless of which method or option you choose in the Calculate tab. Refer to the Acrobat Calculate Tab PDF file in the folder for this chapter. Refer to Figure 6-2.

Figure 6-2. The Calculate tab is common to all three methods we will discuss shortly

Sum Value

In the Calculate tab, select the “Value is the…” button and pick sum (+) from the dropdown menu. Notice there are field names of some of the fields in the form in the grey area (Figure 6-3).

Figure 6-3. Entering the sum value into the Calculate tab

In this example and Figure 6-3, you are getting data or value from two fields: Object 1Sum and Object 2Sum. They add together in the field TotalSum to offer a result. These values were entered by selection using the Pick button.

Simplified Field Notation

Now let’s look at simplified field notation. Notice in the Calculate tab in Figure 6-4 that the button called Simplified Field Notation is selected.

Figure 6-4. Entering the simplified field notation into the Calculate tab

The second way of accomplishing this is SFN, which is common to a program like Microsoft Excel. While this is similar to the value sum example, there are differences. In the previous sum example, you could have spaces between the words in the fields. However, Object 1Sum in SFN must be written as Object1Sum. There can be no breaks using SFN. This rule is very strict. Any break in the name of the field and it will not calculate. If you need a break, use an underscore (_), as in Object1Sum_2 or use what is known as the camel method where each new word is capitalized, but with no breaks (ObjectSum).

Another difference to SFN is the addition of a plus symbol (+) to show that you are adding these two field values within the field TotalSum_2. If you were multiplying, you would use an asterisk (*), subtraction a minus (-), and division a slash (/). If you’ve ever taken algebra, you’ll be familiar with parentheses (). Whatever occurs within them happens first before the calculation continues. Refer to Figure 6-5.

Figure 6-5. Entering the SFN into the Calculate tab for a more complex calculation

To type this code into the editor, you must first click the Edit button. Then you can type. When done, click OK to exit.

Here you can see (Object1MoreComplex*2) + (Object2MoreComplex-7) = TotalMoreComplex

If you put numbers into these fields, this should be your answer :

(5*2) + (10-7) = 13

JavaScript Custom Calculation Script

The final method we will look at is a custom calculation script . Figure 6-6 shows the “Custom calculation script” button selected.

Figure 6-6. Entering the custom calculation script into the Calculate tab

To type this code into the editor, you must first click the Edit button. Then you can type. When done, click OK to exit.

In the case of JavaScript, you can again see that there are similarities and differences in the way the code is set up. In order to translate the fields into the language of JavaScript, you need to use variables to hold the fields. Variables act as information containers. In JavaScript, the word variable uses the short form var. After the word var you add a name. In this example, to keep it simple, let’s use the name a. This variable called a will now hold whatever value comes into the text field Object1Sum_3. Once a variable is named the first time, it does not need to have the word var attached and can be used anywhere in the script as just a. To ensure that the number input will follow through correctly, add this.getField which means “get the data in this field.” At the end of the variable, use a semicolon (;) to indicate that that is the end of this variable statement. The same is true for the second variable, b.

The final part of the script is

event.value = a.value + b.value;

It’s very similar to the SFN example. However, you need to add the .value on the end of each variable to remind Acrobat that you want the value of each and the final value to be added in the final field. The final field, TotalSum_3, is represented by event.value. In this final field, the event of the addition taking place is the result. It is important to note that the final field does not need a variable name because of the way Acrobat contains the script within the final field.

Where the naming of variables is concerned, it’s OK to have the names longer than one letter, like a. You can give them more meaningful names like age or sum. In the final example it would be written like this:

event.value = age.value + sum.value                          ;

A few other things to remember about variables are

• All JavaScript variables must be identified with unique names.

• Names can contain letters, digits, and underscores.

• Names must begin with a letter.

• Names are case sensitive (y and Y are different variables).

• Reserved words (like JavaScript keywords) cannot be used as names. I would not create a variable like var event because event is a key JavaScript word used in the final event. For example, event.value = age.value + event.value; might not function since event.value has already been used once.

Final Thoughts

You have seen three ways in which addition can be done: Value, simplified field notation, and a JavaScript custom calculation script. However, which one is right for your project? Do you need to learn Acrobat JavaScript at all?

In most simple calculation projects, I recommend using Value or SFN in various parts of the form. However, if you take a look at the example, you will see Value and SFN do not equally cover all issues. For Value, you cannot subtract or divide. SFN cannot find minimum or maximum numbers. In this case, you may have to use a combination of both these calculations in your form.

For example,

var q = this.getField("Object1Minimum_3");
var r = this.getField("Object2Minimum_3");
event.value=Math.min(q.value,r.value);

You can use the JavaScript math formula Math.min to get my minimum number similar to the value example. You could use Math.max to get the maximum number. There are other math formulas that are not available to us via Value or SFN, but are with JavaScript:

• Math.abs(x): Returns the absolute value of x.

• Math.acos(x): Returns the arccosine of x, in radians.

• Math.asin(x): Returns the arcsine of x, in radians.

• Math.atan(x): Returns the arctangent of x as a numeric value between -PI/2 and PI/2 radians.

• Math.atan2(y,x): Returns the arctangent of the quotient of its arguments.

• Math.ceil(x): Returns x, rounded upwards to the nearest integer.

• Math.cos(x): Returns the cosine of x (x is in radians).

• Math.exp(x): Returns the value of Ex, where E is Euler’s number.

• Math.floor(x): Returns x, rounded downwards to the nearest integer.

• Math.log(x): Returns the natural logarithm (base E) of x.

• Math.PI: Gives the formula of p.

• Math.pow(x,y): Returns the value of x to the power of y.

• Math.random(): Returns a random number between 0 and 1.

• Math.round(x): Rounds x to the nearest integer. Example: Round up a subtotal.

• Math.sin(x): Returns the sine of x (x is in radians).

• Math.sqrt(x): Returns the square root of x.

• Math.tan(x): Returns the tangent of an angle.

From www.w3schools.com/jsref/jsref_obj_math.asp .

One final thing, which you could not do in this form without JavaScript is format the number 0. Sometimes on a form you do not want the 0 to be present if no calculation has been added to the first two fields; you just want it blank. Refer to Figure 6-7.

Figure 6-7. Adding a validation script into the Validate tab of the Total field. Before and after adding the script.

This looks better.

Along with the Calculate tab script, enter the following into your Validate tab:

// Custom Validate script for text field
if (event.value == 0) event.value = "";

To start off this script in text field Object1Sum_3, write a comment to remind yourself what you’re doing.

A double slash (//) always starts off a comment. They can be written anywhere in JavaScript and will not affect the calculations. Consider them a place for helpful reminders.

Another type of commenting you can use is for longer, paragraph-sized comments:

/* This type of comment is for lots of text */

However, I generally prefer to use // due to the small space Acrobat provides .

if (event.value == 0) event.value = "";

if (event.value === 0) event.value = "";

//Sum Validation to insure 0 is not missing from an actual calculation
if (a.value !== a.defaultValue && b.value !== b.defaultValue) {
event.value = a.value*1 + b.value*1 ;
} else {
event.value ="" ;
}

Summary

In this chapter, you looked at the three ways you can add calculations to your form fields using the Calculate tab.

• Value

• Simplified field notation

• JavaScript

While each example became progressively more complex, a broader range of possibilities opened up as you moved toward JavaScript.

You also saw how adding JavaScript to your Validation tab made it possible to see when the Total field was being utilized and when it was not. Giving clients accurate form information updates is important.

In the next chapter, you will explore how custom JavaScript can affect the Format tab when it comes to

• Number

• Percentage

• Date

• Time