Default Parameter Values

Sometimes it is useful to set a default value for a parameter. For example, when the parameter value is often repeated. 

Default parameter values allow us to call a function without having to specify all parameter values. If a parameter value with a default value is not specified, its default value is used. We specify the default value of a parameter when defining the function using the = operator. For example:

function greet(name="world") {
    console.log("Hello, " + name);
}

This function has one parameter name with a default value of "world". When we call the function without the parameter value:

greet(); // Prints: Hello, world

The function uses the default value and prints Hello, world.

When we call the function with the parameter value:

greet("Carl"); // Prints: Hello, Carl

The function uses the specified value and prints Hello, Carl.