We know that in JavaScript functions have parameters

function(parameter1, parameter2, parameter3) {
    code to be executed
} // here function is the name of the function

Rules for the parameters

• We do not specify data types for parameters in JavaScript function definitions.
• We do not perform type checking on the passed arguments in the JavaScript functions.
• We do not check the number of arguments received in the JavaScript functions.

Parameter Defaults If we call a function with missing arguments (less than declared in the code), the missing values are set to: undefined Consistently this is acceptable, but sometimes it is better to assign a default value to the parameter: Example

function Function(a, b) {
    if (b=== undefined) {
          b= 0;
    }
}

In this we are setting a default value to a function parameter that is zero.

If a function is called with many arguments (more than declared), these arguments can be reached using the arguments object.