Javascript – Pure vs Impure functions

I have gone through the definitions of the two like:

Pure functions are ones that do not attempt to change their inputs, and always return the same result for the same inputs.

Example

function sum(a, b) {
  return a + b;
}

And Impure function is one that changes its own input.

Example

function withdraw(account, amount) {
  account.total -= amount;
}

Definitions and Code snippets taken from ReactJs official docs.

Now, can somebody tell me, how can I make some mistakes in React/Redux, to use impure functions where pure functions are required.

Source: ReactJs