Any function whose output is ONLY dependent on its input.
In coding, Functions may be pure or impure. Impure functions produce outputs that depend on not only their inputs, but also rely on some ambient variable or some sort of 3rd party “state”.
Examples
//#Impure
let carColor = "blue";
function carDesc(){
return `Wow! a ${carColor} car!`
}
//#Pure
function carDesc(color){
return `Wow! a ${color} car!`
}Often, impure functions are class methods dependent on the state of some class instance properties.