CODEWITHSUNDEEP
javascript
Apollo
Apollo

Reputation: 9062

Functions stored in variables? Javascript

Could somebody please explain what this notation is in javascript? What is function(d) doing? In this program it seemse that x is called by the following, but I have no idea what any of this means. Thanks in advance...

x = function(d) { return d.x * width / mx; };

// later....
 x({x: .9}); // call

Upvotes: 4

Views: 25437

Answers (2)

Eswar Rajesh Pinapala
Eswar Rajesh Pinapala

Reputation: 4911

.9 is a value of the property x of the object(d) being passed into the function.

In the function, d = {x:9}(object) , now when you ask for d's property(x) Value (using DOT notation), it returns the value for the property x.

so d.x returns 0.9!

So you would ask me how did i pass the value of the property into the function-X in the first place, well thats what we did when we dis this -> x(objectBeingSent); where objectBeingSent is {x: .9}.

Anonymous functions are functions that are dynamically declared at runtime. They’re called anonymous functions because they aren’t given a name in the same way as normal functions.

Anonymous functions are declared using the function operator. You can use the function operator to create a new function wherever it’s valid to put an expression. For example you could declare a new function as a parameter to a function call or to assign a property of another object.

The function operator returns a reference to the function that was just created. The function can then be assigned to a variable, passed as a parameter or returned from another function. This is possible because functions are first class objects in javascript.

Here’s an example where a function is declared in the regular way using the function statement:

 function eatCake(){
     alert("So delicious and moist");
 }
 eatCake();

Here’s an example where the same function is declared dynamically using the function operator:

 var eatCakeAnon = function(){
     alert("So delicious and moist");
 };
 eatCakeAnon();

See the semicolon after the second function's closing bracket? }; You use a semi-colon after a statement. This is a statement: 

var eatCakeAnon = function(){
         alert("So delicious and moist");
     };

Source

P.S. Best explanantion that i could find!

Upvotes: 6

Dondi Michael Stroma
Dondi Michael Stroma

Reputation: 4800

It's called an anonymous function. The function takes an object in the form of {x: number} as an argument and does some math on number.

Upvotes: 1

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