Impure vs Pure functions

Question

What is the difference between impure and pure functions?

Mahesh Verma · Answer

Hello Reena, Impure functions are those functions which modifying their argument like function calculate(input) { input.count++; } In the above function, if the initial value of count is 0 and we call this function 10 times then the value of count is 10. However, on the other side, if we talk about Pure Functions, we cannot modify the value, we can return a new value each time, like function calculate(input){ return {count : input.count+1}; } Hope, this code will help you to understand difference between them.

Jignesh Kumar · Answer

Hi Reena, Please find below links, https://toddmotto.com/pure-versus-impure-functions https://blog.angularindepth.com/the-essential-difference-between-pure-and-impure-pipes-and-why-that-matters-999818aa068

Muthu Kumar · Answer

Here is an alternative example and description for Pure and Impure Functions https://stackoverflow.com/questions/22395311/difference-between-pure-and-impure-function https://www.quora.com/What-is-the-difference-between-a-pure-and-an-impure-function This solution has been mentioned above url, Characteristics of Pure Function: The return value of the pure func­tions solely depends on its arguments Hence, if you call the pure func­tions with the same set of argu­ments, you will always get the same return values. They do not have any side effects like net­work or data­base calls They do not mod­ify the argu­ments which are passed to them Char­ac­ter­isitcs of Impure functions The return value of the impure func­tions does not solely depend on its arguments Hence, if you call the impure func­tions with the same set of argu­ments, you might get the dif­fer­ent return values For exam­ple, Math.random(), Date.now() They may have any side effects like net­work or data­base calls They may mod­ify the argu­ments which are passed to them function impureFunc(value){ return Math.random() * value; } function pureFunc(value){ return value * value; } var impureOutput = []; for (var i = 0; i impureOutput.push(impureFunc(5)); } var pureOutput = []; for (var i = 0; i pureOutput.push(pureFunc(5)); } console.log( "Impure result: " + impureOutput); // result is inconsistent however input is same. console.log( "Pure result: " + pureOutput); // result is consistent with same input