Rod

Just watched a video on youtube on inheritance by Nathan Wall (might be of interest to someone who struggling like me) and together with the replies I've had here......, I get the inheritance thing now. Thanks to all that have replied to this post.  

well.... using that (your) logic i might as well put 70 in "theResult" in the first place.

I'm not trying to do something in particular with this, i was just wondering "can it be done", and so....now knowing that it can be done, it might come in useful in the future. (not necessarily on a math problem) . I don't doubt your comment that "eval" is inefficient"......i have no idea either way, I'm new to javascript, but... it's available and it worked.

Just in case someone is interested, I managed to get it to work. I've tried passing the "+" without the quotes and then doing toString() on the receiving parameter but that did not work but as it in now, it does work.

function doMath(a,b,doThis){
    return    eval(a.toString().concat(doThis, b.toString()));
}

var theResult = doMath(50, 20, "+");
alert(theResult);

Is there a way of passing arithmetic operators via a functions' parameters and/or arguments. e.g

##########################################################################
function doTheMath(a, b, doThis) {
    return a  doThis  b;    //  have this evaluate to... a + b or a * b ...etc as appropriate.
}

var theResult = doTheMath(4,10, + );     // the "+" could be any of the arithmetic operators.
##########################################################################

I know it's possible to do it with multiple "if" statements or "switch" statement or callbacks (yes..i watched a video on callbacks on...."a well known video sharing website",  but is there an easier (smaller code) way of doing it.

Just curious....I'm a newbe.

Ok... thanks.... I'll have a look on google and youtube. Thank you for your time anyway.

There no real reason, just trying to understand what I've learnt and might be good to know for the future..

I assumed that because "age" property is in the "Person" object prototype, then the myMother object would "inherit" the "age"  property. So... with reference to your last comment, I must be misunderstanding the "inherit" thing.

The script above was copied from this website, under the heading "creating a prototype" and in there is says to use "object constructor function" which is what I have done.

Now this.

The link you gave shows how to create new methods to pre-existing  javascript object. (in your case..... an Array).

Quote from Parent website

"Prototype Properties"

"JavaScript objects inherit the properties of their prototype.

The delete keyword does not delete inherited properties, but if you delete a prototype property, it will affect all objects inherited from the prototype."

so why does the script below work?

<script>
function Person(first, last, age, eye) {
    this.firstName = first;
    this.lastName = last;
    this.age = age;
    this.eyeColor = eye;
}
var myMother = new Person("Sally", "Rally", 48, "green");

delete myMother.age; // apparently... this should not work as "age" (as I understand) has been inherited from the Person prototype.

document.getElementById("demo").innerHTML =
"My father is " + myFather.age + ". My mother is " + myMother.age; 
</script>
myMothe.age  now outputs undefined and that's what i expected.

What am i misunderstanding?

Thank you in advance.