Data Types

Every variable stores some kind of data. That data might be a person's name, a number, a date, a list of products, or even an entire object.

The type of data stored in a variable is called its data type.

Understanding data types is important because different types of data support different operations. For example, you can add two numbers together, but adding two dates doesn't make sense in the same way. Similarly, you can convert text to uppercase, but you can't convert a number to uppercase.

One of the great features of ColdFusion is that it is dynamically typed. You don't have to declare a variable's data type before assigning a value. ColdFusion automatically determines the appropriate type based on the value you assign.

By the end of this lesson, you'll understand the most common ColdFusion data types and know when to use each one.

Learning Objectives

After completing this lesson, you'll be able to:

• Understand what a data type is.
• Identify the common ColdFusion data types, including null.
• Store different types of values in variables, in both CFScript and Tag Syntax.
• Check a variable's data type with isNumeric(), isBoolean(), isDate(), and isValid().
• Know when to use each data type.

What Is a Data Type?

A data type tells ColdFusion what kind of value a variable contains. For example:

Dynamic Typing

Unlike Java or C#, you don't specify a variable's type. Simply assign a value.

<cfscript>

    name = "Sandeep";
    age = 28;
    salary = 55000.75;
    isAdmin = true;

</cfscript>

One more thing worth knowing: internally, ColdFusion treats every value as an object under the hood, running on the JVM. As a beginner you don't need to think about that — just assign a value the normal way, and ColdFusion handles the rest.

Common ColdFusion Data Types

String

A String stores text.

Numeric

Numeric values include whole numbers, decimal numbers, and negative numbers. Numbers support mathematical operations.

Boolean

A Boolean represents one of two values, true or false, and is commonly used in conditions.

Date & Time

ColdFusion has excellent built-in support for dates.

<cfscript>

    today = now();

    writeOutput(today);

</cfscript>

<cfset today = now()>

<cfoutput>
    #today#
</cfoutput>

Array

An Array stores multiple values in order.

Structure (Struct)

A Struct stores data as key-value pairs, similar to a JSON object or a dictionary in other languages.

Query

A Query stores the rows and columns returned by a database call — the result of running a <cfquery> tag or calling queryExecute(). A query can contain multiple rows and columns, and you can loop over it just like an array of records.

<cfscript>

    employees = queryExecute(
        "SELECT firstName, lastName FROM Employees"
    );

</cfscript>

Component (Object)

A Component is created from a .cfc file. Objects contain properties and methods.

<cfscript>

    user = new User();

</cfscript>

Binary

Binary data represents files instead of readable text — images, PDFs, ZIP files, videos.

Null (Adobe ColdFusion 2021+)

Modern Adobe ColdFusion supports a real null value, meaning "no value assigned," distinct from an empty string or a zero. Older ColdFusion versions didn't have true null support — an undefined variable simply threw an error instead.

<cfscript>

    value = javaCast("null", "");

</cfscript>

Checking the Data Type

ColdFusion provides several isXxx() functions to check a variable's type — the ones you'll reach for most often are isNumeric(), isBoolean(), and isDate(), plus the more general-purpose isValid().

Using isNumeric()

Using isBoolean()

Using isDate()

Using isValid()

isValid() is more generic than the others — it can check many different kinds of values, not just numbers, booleans, and dates, using a type name you pass in as a string (like "email", "numeric", "date", and several more).

Dumping Variables

During development, writeDump() (CFScript) and <cfdump> (tags) help you inspect a variable's type and contents.

<cfscript>

    employee = {
        name = "John",
        age = 30
    };

    writeDump(employee);

</cfscript>

<cfset employee = {
    name = "John",
    age = 30
}>

<cfdump var="#employee#">

Real-World Example

Visual Overview

1. Storing Numbers as Text

age = "25";

Although ColdFusion can often convert it automatically, it's better to store numbers as numbers:

age = 25;

2. Using Quotes with Boolean Values

isAdmin = "true";

isAdmin = true;

3. Confusing Arrays and Structs

colors = ["Red","Green","Blue"];

colors = {
    primary = "Red"
};

4. Assuming Variable Types Never Change

Because ColdFusion is dynamically typed, the same variable can store different data types:

value = 10;
value = "Ten";
value = true;

Best Practices

• Store numbers as numbers.
• Store Boolean values as true or false.
• Use Arrays for ordered collections.
• Use Structs for related key-value data.
• Use meaningful variable names.
• Use isNumeric(), isBoolean(), isDate(), or isValid() to check untrusted input before using it.
• Use writeDump() or <cfdump> while learning to inspect variables.

Quick Revision

Interview Questions

Summary

In this lesson, you learned what data types are and why they are important. You saw that ColdFusion automatically determines a variable's type based on the assigned value, making the language easy for beginners while remaining powerful for large applications.

You also learned the most commonly used data types — String, Numeric, Boolean, Date & Time, Array, Struct, Query, Component (Object), Binary, and Null — along with how to inspect variables using writeDump() and validate data using functions like isNumeric(), isBoolean(), isDate(), and isValid().

A solid understanding of data types is the foundation for writing reliable ColdFusion applications, because almost every program stores, processes, and displays different kinds of data.

What's Next?

The next lesson covers Comments — why they matter, single-line and multi-line comments, HTML comments vs. ColdFusion comments, and how to comment code in both CFScript and Tag Syntax.