Helping me in writing a simple function, passing a parametrer value 0 when not declared

I don't know what is the best way to write it and how to... I have a function like

function myFunc(myVal1, myVal2){/*... various things ...*/};

where myVal1 and myVal2 are numbers

Sometimes I want to be able to recall the function passing only one parameter just by calling myFunc(myVal1). Doing so I want that myVal2 would have a standard value, if not declared, of 0.

I was thinking to write something

function myFunc(myVal1, myVal2){
    if(myVal2 == NaN)
         myVal2 = 0;
    }
}

But I don't believe that it is the right way to do开发者_StackOverflow社区 it. Thx very much for the help!

---

Arguments that are not set have type undefined, test for it like this.

function myFunc(myVal1, myVal2){ 
    if(typeof myVal2 == "undefined") 
         myVal2 = 0; 
    //the rest of the function goes here
} 

---

function myFunc(myVal1, myVal2){ 
    // if myVal2 is defined, keep the value, otherwise assign 0
    myVal2 = myVal2 || 0; 
} 

should do the trick.

more ways to Rome (besides typeof myVal2 == "undefined"):

function myFunc(myVal1, myVal2){ 
    // if myVal2 is defined, keep the value, otherwise assign 0
    // using a ternary operator
    var myVal2check = myVal2 ? myVal2 :  0; 
}


function myFunc(myVal1, myVal2){ 
    // if myVal2 is defined, keep the value, otherwise assign 0
    // if myVal2 needs to be an integer
    myVal2 = parseInt(myVal2,10) ||  0; 
}

function myFunc(myVal1, myVal2){ 
    // if myVal2 is defined, keep the value, otherwise assign 0
    // using a regexp to determine the 'undefinedness'
    var myVal2check = String(myVal2).match(/undef/i) ? myVal2 :  0; 
}

and finally, especially for David Mårtensson

function myFunc(myVal1){ 
    // no myVal2 defined in the parameter section
    var myVal2check = window.myVal2 ? myVal2 :  0;
}

---

if (!myVal2) {
  myVal2 = 0;
}

If you want myVal2 to default to anything other than 0, you have to be more explicit, as 0 evaluates to false. So:

if (!myVal2===undefined) {
  myVal2 = 3;
}