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I stumbled upon this block of code and don't really see the need for returning a function when the outer function doesn't take any arguments?
var percent = (function() {
var fmt = d3.format(".2f");
return function(n) { return fmt(n) + "%"; };
})()
Am I missing something or can it be rewritten as:
var percent = function(n) {
return d3.format(".2f")(n) + "%";
}
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A factory function can be defined as a function that creates an object and returns it. It is similar to constructor functions/class functions. The factory function is a very useful tool in JavaScript since it returns the object of any class directly.
Introduction to the factory functions in JavaScriptWhen a function creates and returns a new object, it is called a factory function. The createPerson() is a factory function because it returns a new person object. By using the factory function, you create any number of the person objects without duplicating code.
Factory functions are functions that return objects. We can use factory functions and closures to have private variables and private functions, only exposing what we want to our consumer through the object we return, all while avoiding the this keyword. Factories make for easy composition of values and functionality.
3. Which of the following is a factory function? Explanation: jQuery() is a factory function rather than a constructor: it returns a newly created object but is not used with the new keyword. jQuery objects define many methods for operating on the sets of elements they represent.
It can, but then you are calling d3.format(".2f") each time instead of once only. Depending on what the function is doing and how often it is called, this could add an additional performance overhead.
With the IIEF (immediately invoked function expression) returning the closure, you are "caching" fmt for all future uses of percent.
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