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Beginner’s question


In the following example :

function makeAddFunction(amount) {
function add(number) {
return number + amount;
return add;

var addTwo = makeAddFunction(2);
var addFive = makeAddFunction(5);
show(addTwo(1) + addFive(1));

The answer is 9. I understand very well that makeAddFunction(2)’s value is 2 and is used to replace the term (amount) in the first line and the same applies to makeAddFunction(5) for 5 as a value.

What I cannot explain though is how the program uses 1 as a value for add(number).There is no link at first glance between function add(number) and addTwo(1) or addFive(1). Can anyone show me how the program sets 1 as a value for those last two variables?

Thank you!


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5 Comments(s)

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@007JulienMar 26.2013 — What is the function add(number) ?
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@laurentXauthorMar 26.2013 — You see, this is where I get confused. The (1) in addTwo(1) and addFive(1) are assigned to number in add(number) but I don't understand how this variable is assigned. Maybe it's the syntax that I don't understand. Can anyone help me on this?

Thanks again,

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@007JulienMar 26.2013 — Sorry I have not seen ! Two remarks :

1/ - You have build a closure,

2/- number, which is an argument of the function, has the value 1. It's the same thing with foobar then one would expect undefined ???
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@grumpyOleManMar 26.2013 — As has been pointed out it is a closure that makes use of an inner function.

the variables have a memory to the original numbers to use when you call it with the 1

the two keyword to use in searching will be

closure and inner function

just to start you off

Copy linkTweet thisAlerts:
@laurentXauthorMar 26.2013 — Thank you guys for your answers. This stuff is new to me, I will take some time to read further in order to understand the concepts. I get the closure part.

What I still don't understand is how the program sets 1 a the variable for number. As far as I can understand, nothing states in the program the value of number. Actually, something does but I can't figure out what it is.

Thanks again,



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