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JavaScript JavaScript Basics (Retired) Creating Reusable Code with Functions Create a max() Function

Tobi Ogunnaike
Tobi Ogunnaike
2,242 Points
Posted by Tobi Ogunnaike
Tobi Ogunnaike
2,242 Points

When calling a function that has an argument, why is it that sometimes you need to specify the parameter..

When calling a function that has an argument, why is it that sometimes you need to specify the parameter and sometimes you don't

See these two examples from code challenges I've solved-

function max(larger, smaller) {
  if(parseInt(larger) > parseInt(smaller)){
    return parseInt(larger);}
  else {return parseInt(smaller)}
}
alert (max());

In the above case , the max() function is called without me needing to write 

alert( max(larger, smaller)

However in a prior code challenge

function returnValue (drink){
  return drink}
returnValue('coffee');
var echo = returnValue('coffee');

Or do I have to ALWAYS have to specify a parameter when calling a function because the browser would not otherwise know what the argument is?

I'm confused and I appreciate any help thanks!

mickey Odunikan
mickey Odunikan
4,983 Points
mickey Odunikan
mickey Odunikan
4,983 Points

Not sure if you put on the entire code but when calling a function it is only necessary to add in parameter if the function needs that information. The function may need user input or other information from previously written code in order to work the way you want.

hope that helps

1 Answer

moonshine
moonshine
8,449 Points
moonshine
moonshine
8,449 Points

JavaScript is forgiving because leaving off arguments in languages like C++ would cause errors. On a side note, the parameters you give a function refer to the indexes of an array called arguments.

function foo() {
    console.log(arguments[0]);
}
console.log(foo(2)); /* Prints 2 */

function boo(var_a) {
    console.log(var_a === arguments[0]);
}
boo("text"); /* Prints true */

Arguments that are not passed to a function will simply be undefined, and as long as your function doesn't try to do something like undefined.charAt(2) it will run without errors.

If parseInt(undefined) === NaN then calling max would look like:

function max(undefined, undefined) {
    if (NaN > NaN){
        return NaN;
    } else {
        return NaN;
    }
}
alert (max()); /* Alerts NaN. */

if we replace the parameters with their actual values.