Do I need to specify parameter in Javascript closure -

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<!doctype html> <html> <body>      <p>changing local variable.</p>     <p id="demo"></p>      <script>         var add = (function () { /* need put x in statement?                           "var add = (function(x) { " */                   var counter = 0;                   return function (x) {return counter+=x}         })()          add(10);         add(15);         alert(typeof(add));         document.getelementbyid("demo").innerhtml = add(20);     </script> </body> </html>

i understand in example above, add assigned return value of self invoking function.

the self-invoking function runs once. sets counter 0 (0), , returns function expression.

my question why function isn't defined like:

var add = (function(x) { .... }()

because you're not passing in arguments:

//              receive arguments... //                  v var add = (function(x) { .... }() //^ //that pass in here.

this self invoking function returns function. it's function (the returned function), accepts parameter x.


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