How to pass the value 'undefined' to a function with multiple parameters?

Question

I want to pass the value of \'undefined\' on a multiple parameter function but without omitting the parameter.

What do I mean with \"without omitting the paramet

Answer 1

You can use apply and an array of parameters to pass "undefined" as one of the parameters. For example, you wanted to pass parm1 as "undefined":

function myFunction (parm1, parm2) {

    if(typeof (parm1) === "undefined"){
        alert("parm1 is undefined")
    }

    if(typeof (parm2) === "undefined"){
        alert("parm2 is undefined")
    }

}

var myParameters = [undefined, "abc"];

myFunction.apply(valueForThis, myParameters );

Answer 2

myFunction(undefined,"abc"); this way should work, what is the problem?

see here

Here is undefined documentation from mozilla, supported by all browsers

Answer 3

Try to use this method if you plan on adding an indefinite amount of parameters:

function myFunc(params) {
    // Define default values
    var name = 'John';
    var age = '40';
    // You can loop through them
    for (var p in params) {
        alert(p + ':' + params[p]);
    }
    // And read them in like this
    if (typeof params.name != 'undefined') {
        name = params.name;
    }
    if (typeof params.age != 'undefined') {
        age = params.age;
    }
    alert(name + ' ' + age);
}

alert('test1');
myFunc({name:'Bob', age:'30'});
alert('test2');
myFunc({name:'Bob'});

Answer 4

You need to handle the function call with undefined variable in the function code itself in one of the following way :-

 function myFunction (parm1, parm2) {

         if (parm1 !== undefined) {
             // execute code if 1st param is undefined
        }

         if (parm2 !== undefined) {
             // execute code if 2 param is undefined
        }

        // execute other part of code

    }

Now you can call the above function in following ways:-

myFunction(undefined,"abc"); // with 1st param value not known

myFunction("cde",undefined); // with 2nd param value not known

myFunction("cde","abc");  // with both param value known

Answer 5

A better approach might be passing Object with named attributes and then look for those specific attribute values. This way you don't have to be dependent on number of arguments.
Example: Object.dummy

Answer 6

I just had an idea and it seems to work:

var undf;

myFunction(undf, "abc");

I am sure there are better ways, however I post this