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Article 4: Using Boolean Operators

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CallFireXML uses JavaScript at certain points in the IVR — particularly in setvar tags and in if tag comparison expressions. Here are some of the standard Boolean (logical) operators you can use.

The relational operators are for comparisons. Please note that the single equal sign (=) defines the contents of a variable. For example, the statement "x = 1" populates the variable x with the number 1. The statement "x = 'elephant' " puts an elephant (or at least the string 'elephant') into the variable x. So a single equal sign does not perform a comparison, it is used for setting a variable's value. Instead, to perform a comparison we use the double equal sign (==).

So the relational operators are:

<, <=, >, >=, !=, ==

These are 'less than', 'less than or equal to', 'greater than', 'greater than or equal to', not equal to', (more about that one in a moment), and 'equal to', respectively. Look again at 'not equal to' (!=) — the exclamation point means "not," so technically, '!>' would mean "not greater than'. The ! is useful in the following multiple-condition scenarios.

What if a particular action needs to be taken only if multiple conditions are true? You can use logic operators to handle multiple conditions. There are three logic operators: &&, || and !.

'&&' is logical 'and' — && combines two Boolean values and returns a Boolean which is true if and only if both of its operands are true. For instance:

b = 3 > 2 && 5 < 7; // b is true

b = 2 > 3 && 5 < 7; // b is now false

'||' is logical 'or' — || combines two Boolean variables or expressions and returns a result that is true if either one or both of its operands are true. For instance:

b = 3 > 2 || 5 < 7; // b is true

b = 2 > 3 || 5 < 7; // b is still true

b = 2 > 3 || 5 > 7; // now b is false

The last logic operator is ! which means 'not' (see above). It reverses the value of a Boolean expression. Thus if b is true, !b is false. If b is false, !b is true.

b = !(3 > 2); // b is false

b = !(2 > 3); // b is true

These operators allow you to test multiple conditions with ease. For example, we can write an if tag as follows:

 

A real-world example might use the global time stamp to define an "after business hours" action:

 

In the above example, '< 7' means 'less than (earlier than) 7:00 AM' and '> 18' means 'greater than (later than) 6:00 PM.'

 

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