#handleFileSelect is an Impure Function handleFileSelect has in your code snippet a dependence to fr which is decleraded outside of the function. To make the function pure you can pass fr as argument.

#Put Side Effects Into a Wrapper

#Either You Can Parse to a JSON or Not.. In the following I want to introduce a functor calles Either which is split into to functors Left and Right. If we can parse a string succesfully we will return a Right with the parsed value otherwise we will return Left with an error message.

handleFileSelect is an Impure Function

handleFileSelect has in your code snippet a dependence to fr which is decleraded outside of the function. To make the function pure you can pass fr as argument.

Put Side Effects Into a Wrapper

Either You Can Parse to a JSON or Not..

In the following I want to introduce a functor calles Either which is split into to functors Left and Right. If we can parse a string succesfully we will return a Right with the parsed value otherwise we will return Left with an error message.

#handleFileSelect is an Impure Function handleFileSelect has in your code snippet a dependence to fr which is decleraded outside of the function. To make the function pure you can pass fr as argument.

#Put Side Effects Into a Wrapper

The function writeInfo contains side effects because we access the DOM. We could wrap the DOM functions in to a wrapper called IO which will always return a function - always the same function.

#Either You Can Parse to a JSON or Not.. In the following I want to introduce a functor calles Either which is split into to functors Left and Right. If we can parse a string succesfully we will return a Right with the parsed value otherwise we will return Left with an error message.

The free online book mostly-adequate-guide is very good
The series composing-software is a good way to start

#handleFileSelect is an Impure Function handleFileSelect has in your code snippet a dependence to fr which is decleraded outside of the function. To make the function pure you can pass fr as argument.

#Put Side Effects Into a Wrapper

The function writeInfo contains side effects because we access the DOM. We could wrap the DOM functions in to a wrapper called IO which will always return a function - always the same function.

#Either You Can Parse to a JSON or Not.. In the following I want to introduce a functor calles Either which is split into to functors Left and Right. If we can parse a string succesfully we will return a Right with the parsed value otherwise we will return Left with an error message.

The free online book mostly-adequate-guide is very good
The series composing-software is a good way to start

The free online book mostly-adequate-guideh is very good
The series composing-software is a good way to start

The free online book mostly-adequate-guide is very good
The series composing-software is a good way to start