JavaScript Quiz - 2 function questions.

Question

Hello there, 
In the video, Quiz has 2 function questions. I'd like to understand clearly as to how to interpret them when I see or code this. After I watched the video, I can't follow the logic to interpret the codes. This is kinda frustrating for me. : ( Even though I can 'guess' what the answer is but not very nice not to have a full understanding on this. 
Thanks!
X's value:?
var f = function(a , b){
return a + b;
}
var x = f("Hello", "World");
X's value?
var f = function(a, b){
var c = a + b;
return c * 2;
}
var x = f(3, 4);

Jonathan Grieve · Accepted Answer

Hi there Amber.
Let me have a go at explaining these.  :)
```javascript
var f = function(a , b){ return a + b; }
var x = f("Hello", "World");
```
With this one you have a function defined in one variable and with var x you have the function call with passes in arguments to the function.
With the function call you'd get the output HelloWorld.  You might want to put a space at the end of the first string or at the beginning of the second string to get Hello World
javascript
var f = function(a, b){ var c = a + b; return c * 2; }
var x = f(3, 4);

It looks like in this one the value for x is 14.
Functions take parameters with arguments passed in at function call.  The variable c holds an addition calculation which is being multiplied by 2. Just like in the first function the way the function knows how what numbers to calculate is because they're passed in at the function call. 
So it's 3 + 4 which = 7 and multiply the 7 by 2.
I hope this all makes sense.  :)

Amber Tai · Answer

Thanks. :D

Jonathan Grieve · Answer

Hi Amber, 
With regard to your first paragraph there are better ways to work with functions which we learn about when we get into more complex programming.  I'd say if you needed to pass in more than 5 arguments (some might say more or fewer) then we probably need to look for another way to work with functions but this is the most basic level of programming with functions.
You use placeholder variables called parameters and pass in the values in as "arguments" in a function call level.   In your second example, yes a is given the value of "Hello" and b is given the Value of "World."  :-)
With your first paragraph...  I think what you're asking is could the letters a and be in the function parameters be anything else and the answer is yes.  You could actually give default values in there but really all those things are in those parentheses are placeholder variables. 
```javascript
var f = function(a , b){
    return a + b; 
}
```
a and b could be something like 
javascript
var f = function(numberOne , numberTwo){
    return numberOne + numberTwo; 
}

After which you could pass in
javascript
var answer = f(2,2)

which would return 4.   :-)

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Amber Tai

Amber Tai

JavaScript Quiz - 2 function questions.

3 Answers

Jonathan Grieve

Jonathan Grieve

Amber Tai

Amber Tai

Amber Tai

Amber Tai

Jonathan Grieve

Jonathan Grieve

Jonathan Grieve

Jonathan Grieve

Amber Tai

Amber Tai