reduce, some/every, find — simple patterns
Learn reduce for totals, some/every for boolean checks, and find to get the first matching item.
reduce, some/every, find — simple patterns is a free JavaScript Academy lesson on CoddyKit — lesson 2 of 2. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the JavaScript Academy learning path, one of 2 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Intro to reduce & friends
Goal: Turn many values into one with reduce, check arrays with some/every, and get the first match with find.
- reduce: totals
- some/every: quick checks
- find: first match
reduce sum
reduce takes a callback and an initial value. Return the next accumulator each step.
// reduce: sum numbers with an initial value
const prices = [4, 6, 3];
const total = prices.reduce(function (acc, n) {
// Add current number to the accumulator
return acc + n;
}, 0);
console.log("Total:", total);
reduce min
You can compute min or max by comparing the accumulator to each value.
// reduce: smallest number
const nums = [7, 2, 9, 4];
const min = nums.reduce(function (acc, n) {
// Keep the smaller of acc or n
return n < acc ? n : acc;
}, Infinity);
console.log("Min:", min);
some basics
some returns true if any item passes the test.
// some: is there any even number?
const list = [1, 5, 8, 11];
const hasEven = list.some(function (n) {
return n % 2 === 0;
});
console.log("Has even?", hasEven);
every basics
every returns true only if all items pass the test.
// every: are all ages 18+ ?
const ages = [22, 19, 31];
const allAdults = ages.every(function (a) {
return a >= 18;
});
console.log("All adults?", allAdults);
find basics
find returns the first item that matches your test, or undefined if none match.
// find: get the first matching value (or undefined)
const users = [
{ name: "Ayla", active: true },
{ name: "Mina", active: false },
{ name: "Lena", active: true }
];
const firstInactive = users.find(function (u) {
return u.active === false;
});
console.log("First inactive:", firstInactive);
reduce concept quiz
Quick check: Accumulator method.
Recap
Recap: Use reduce for totals or min/max, some to check “any?”, every to check “all?”, and find to grab the first matching item.
Frequently asked questions
Is the “reduce, some/every, find — simple patterns” lesson free?
Yes — the full text of “reduce, some/every, find — simple patterns” is free to read here on the web, and the JavaScript Academy course includes 2 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the JavaScript Academy course, upgrade to CoddyKit PRO.
What will I learn in “reduce, some/every, find — simple patterns”?
Learn reduce for totals, some/every for boolean checks, and find to get the first matching item. You practise JavaScript Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start JavaScript Academy?
No prior experience is required. JavaScript Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 2, so you can start here or from the beginning and move at your own pace.
How long does the “reduce, some/every, find — simple patterns” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this JavaScript Academy lesson?
Yes. Every JavaScript Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- map & filter — essentials
- reduce, some/every, find — simple patterns