Functions can take parameters which are names listed in the function's definition. Parameters allow functions to accept arguments when called, and those arguments can then be used inside the function. For example, a function called sayHello is defined to take one parameter called name, and when called with the argument "Dan", it outputs an alert of "Hi, Dan".

1. Functions can take parameters.
Function parameters are the names listed in the function's definition.
Syntax:
After defining the parameters, you can use them inside the function.
This function takes in one parameter, which is called name. When calling the function, provide
the parameter's value (argument) inside the parentheses.
Function
Parameters
functionName(param1, param2, param3) {
// some code
}
function sayHello(name) {
alert("Hi, " + name);
}
sayHello("Dan");
//Alerts "Hi, Dan"