What Is a VAR Data Type?


Angela Bailey

What Is a VAR Data Type?

A data type is a classification of data that determines the type of values it can hold and the operations that can be performed on it. In programming, variables are used to store and manipulate data. Each variable must have a specific data type associated with it.

Introduction to VAR Data Type

The VAR data type, short for variant, is a special data type that allows variables to hold values of different types. Unlike other strongly typed languages, such as Java or C++, where variables must be declared with a specific data type, the VAR keyword in some programming languages allows for dynamic typing.

Note: The VAR keyword is not available in all programming languages. This article focuses on its usage in JavaScript and Delphi (Object Pascal).

Usage in JavaScript

In JavaScript, the VAR keyword was widely used before the introduction of let and const keywords in ECMAScript 2015 (ES6). Variables declared with VAR are function-scoped and are hoisted to the top of their scope.

  • Example:

function exampleFunction() {
var myVariable = 10;

exampleFunction(); // Output: 10
console.log(myVariable); // Error: myVariable is not defined

In the above example, myVariable is declared using VAR within the exampleFunction(). It can only be accessed within that function and not outside it. If we try to access it outside the function’s scope, we’ll get an error.

Usage in Delphi (Object Pascal)

In Delphi (Object Pascal), the VAR keyword is used to pass variables by reference instead of by value. This means that when passing a variable as a parameter to a procedure or function, any changes made to the variable within the procedure or function will also affect its original value.

procedure ExampleProcedure(var myVariable: Integer);
myVariable := myVariable + 1;

x: Integer;
x := 10;
writeln(x); // Output: 11

In the above example, x is passed as a reference to the ExampleProcedure() using the VAR keyword. Any changes made to myVariable within the procedure will also be reflected in x.


The VAR data type allows for flexibility in handling variables with different types of values. Its usage in JavaScript and Delphi provides programmers with options for dynamic typing and passing variables by reference.

While the VAR keyword is still used in legacy JavaScript codebases, it is generally recommended to use let and const keywords for better code readability and maintainability. In Delphi, the VAR keyword remains an important tool for passing variables by reference.

Note: It’s important to check the documentation of your programming language of choice to understand how it handles variable declaration and scoping.

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