Passing parameters to functions that do not exist or are undefined?

Question

I was wondering what would be better if I had a function that took 4 parameters a, b, c, d, but I had a situation where I did not have a value to pass for param c, but to pass a value to param d so:

function myFunction(a,b,c,d) { //... } myFunction(paramA, paramB, '', paramD); 

Do you pass undefined for the parameter c, and then do a check inside the function or something like that?

Answer 1

Better use Object for me:

 function myFunction( options ) { //... } myFunction({ paramA: "someVal", paramD: "anotherVal" }); 

Then in the function you can check for empty parameters and pass default values:

 function myFunction( options ) { options = options || {}; options.paramA = options.paramA || "defaultValue"; // etc... } 

Answer 2

You can make any optional parameters farther to the right of your function signature, so you can just leave them when you call the function.

 function myFunction(a, b, d, c) { // ... } myFunction(1, 2, 3, 4); // call without 'c' myFunction(1, 2, 3); 

Answer 3

I will find setting the default if it is undefined is the most symplectic / reliable solution

 function myFunction(a,b,c,d) { if (typeof a === 'undefined') { a = 'val'; } if (typeof b === 'undefined') { b = 'val'; } if (typeof c === 'undefined') { c = 'val'; } if (typeof d === 'undefined') { d = 'val'; } } 

Answer 4

Pass null as a parameter that you don't have. undefined bit more specialized, although they will work the same way.

Answer 5

If you know which parameter was passed, you can use the parameter "arguments" to the function. For instance:

  function example(a, b, c, d) { if (arguments.length < 4) { paramC = defaultParam; // something default value for passed C } }