TIL Stateful and stateless
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TAGS: math loops javascript
Programming languages have the notion of “state”. This is a snapshot of a program’s current environment: all the variables that have been declared, functions created and what is currently being executed.
An expression in a programming language can be “stateful” or “stateless”. A stateful expression is one that changes a program’s current environment. A very simple example in Javascript would be incrementing a variable by 1:
var number = 1;
var increment = function() {
return number += 1;
};
increment();The function increment() modifies the variable number directly.
That is a hidden intent, and should be avoided.
This stateless expression, on the other hand, is one that does not modify a program’s environment:
var number = 1;
var increment = function(n) {
return n + 1;
};
increment(number);The function increment() has no values inside of it. It takes a parameter. It's 'pure'.
Via: https://stephen-young.me.uk/2013/01/20/functional-programming-with-javascript.html
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