I am learning javascript and i'm stuck with the concept of function returning function

Question

please help me with below code.I did not understand the functioning of return function(object1,object2).How does the return function in create comparison function() get its parameters.?

var data = [{ name: "Zachary", age: 28}, {name: "Nicholas", age: 29}];

function createComparisonFunction( propertyName) 
{
   return function( object1, object2)
   { 
     var value1 = object1[ propertyName]; 
     var value2 = object2[ propertyName]; 
     if (value1 < value2)
     { 
       return -1; 
     } 
     else if (value1 > value2)
     { 
       return 1; 
     }
     else 
     { 
       return 0; 
     } 
   }; 
}
data.sort( createComparisonFunction(" name")); 
alert( data[ 0]. name); // Nicholas 
data.sort( createComparisonFunction(" age"));
alert( data[ 0]. name); // Zachary

"help you" *how* exactly? What is the problem that you're encountering? — David, Sep 02 '16 at 17:51
I think he's asking what that line of code does. I'm interested to know the answer as well. — Johnny Bones, Sep 02 '16 at 17:53

Saeid · Accepted Answer · 2016-09-02T18:30:33.620

You can assume that sort function is similar to the below code.

function sort( comparefunction )
{
  ...
  if ( comparefunction(obj1, obj2 ){
    // do stuff
  }
}

Now because comaprefunction itself is something like createComparisonFunction("name") you will have something like this in the end: createComparisonFunction("name")(obj1, obj2) which name is the input for createComparisonFunction and obj1, obj2 are the inputs for the nameless function.

score 0 · Answer 2 · answered Sep 02 '16 at 18:45

0

When the sort() method compares two values, it sends the values to the compare function, and sorts the values according to the returned (negative, zero, positive) value.

answered Sep 02 '16 at 18:45

Kiran Varma Lova

1
2

I am learning javascript and i'm stuck with the concept of function returning function

2 Answers2