Immutable Data Patterns
Pure Updates
Return a new value from a function.
Pure Updates
pure_update.js
const bonus = 2;
function addBonus(score, extra) {
return score + extra;
}
const nextScore = addBonus(20, bonus);
const report = "score=" + nextScore;
console.log("bonus=" + bonus);
console.log("report=" + report);
pure-update
A pure update function returns the next value from its inputs. It does not change outside state, which makes the trace easier to reason about.