In JavaScript, there are three ways to define a variable. The var JavaScript variables statement is used to define a variable and, if desired, to set the variable's value. Variable declarations are handled before the code is executed. The const variable employs a function that prevents users from altering the object on which it is invoked. When a function is marked as const, it can be used with any object. The let variable indicates that the variable, such as a counter in a loop or a value swap in an algorithm, may be reassigned. It also indicates that the variable will only be utilized in the block in which it is defined.