every() checks whether all elements in an array satisfy a condition, short-circuiting to false the moment one fails. It is the universal-quantifier counterpart to some(), and a vacuous-truth gotcha on empty arrays trips up many developers.
1Array.prototype.every() | JavaScript Tutorial - In-Depth Guide Part 1
every() returns true only if every single element satisfies the callback ā it returns false the instant one element fails.
const allAdults = users.every((u) => u.age >= 18);All Must Match
2Array.prototype.every() | JavaScript Tutorial - In-Depth Guide Part 2
every() short-circuits on the first failing element, skipping evaluation of the callback on the rest of the array.
[1, 2, -3, 4].every((n) => {
console.log(n);
return n > 0;
});
// logs 1, 2, -3 ā stops once -3 failsShort-Circuits on Failure
3Array.prototype.every() | JavaScript Tutorial - In-Depth Guide Part 3
On an empty array, every() always returns true ā a classic case of 'vacuous truth' that surprises many developers.
[].every((n) => n > 1000); // true (!) ā vacuously trueVacuous Truth
4Array.prototype.every() | JavaScript Tutorial - In-Depth Guide Part 4
every() is the standard tool for validating that an entire dataset meets a requirement before proceeding, like confirming every form field passed validation.
const canSubmit = Object.values(fields).every((f) => f.valid);Validating a Whole Set
5Array.prototype.every() | JavaScript Tutorial - In-Depth Guide Part 5
Because of the vacuous-truth behavior, always guard for an empty array explicitly if 'all pass' should not be true when there's nothing to check.
const allValid = fields.length > 0 && fields.every((f) => f.valid);Guarding the Empty Case
6Step-by-Step Breakdown
every() returns true only if every single element satisfies the callback ā it returns false the instant one element fails.
every() short-circuits on the first failing element, skipping evaluation of the callback on the rest of the array.
On an empty array, every() always returns true ā a classic case of 'vacuous truth' that surprises many developers.
Checkpoint: What does [].every(n => n > 1000) return?
- ātrue, because there are no elements to fail the check
- āfalse, because no elements actually satisfy the condition
every() is the standard tool for validating that an entire dataset meets a requirement before proceeding, like confirming every form field passed validation.
Because of the vacuous-truth behavior, always guard for an empty array explicitly if 'all pass' should not be true when there's nothing to check.
Checkpoint: If a feature requires "at least one field AND all fields valid," is fields.every(f => f.valid) alone sufficient?
- āYes, every() already checks for that
- āNo, an explicit length check is also needed
Next, we'll explore 'The find() Method'.
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Browser Support
Fully supported.
Fully supported.
Fully supported.
Fully supported.
Accessibility (A11y)
1Guard every()-Based "All Complete" Announcements Against Empty States
An accessible progress indicator announcing 'All steps complete' based on `steps.every(s => s.done)` should also check `steps.length > 0`, so a page that hasn't loaded its steps yet doesn't incorrectly announce completion to screen reader users.
SEO Implications
- 1
No Direct SEO Effect
every() is a validation/logic tool; its SEO relevance is limited to preventing incorrect conditional rendering logic in server-rendered pages.
Best Practices
Always Combine every() with a Length Check When Emptiness Should Not Auto-Pass
Relying on every()'s vacuous-truth default for validation logic can silently let an empty dataset "pass" a check that was meant to require at least one valid item.
Use every() for Fail-Fast Validation of Large Collections
It stops on the first invalid item instead of always scanning the whole array, which matters when validating large datasets where most failures happen early.
Frequent Bugs
A "select all" checkbox that checks `items.every(i => i.selected)` incorrectly shows as checked when the items array is empty, since every() vacuously returns true.
Add an explicit `items.length > 0 &&` guard before the every() check so an empty list is correctly treated as "nothing is selected."
Assuming every() evaluates the callback on every element regardless of outcome, and relying on a side effect inside the callback to run for the whole array.
Remember every() short-circuits on the first failure ā any side effects placed inside the callback are not guaranteed to run for elements after the first failing one.
Real-World Examples
Validating an Entire Multi-Step Form
A multi-step checkout flow needed to enable the final "Place Order" button only once every step had been completed and validated.
const canPlaceOrder = steps.length > 0 && steps.every((step) => step.isComplete && step.isValid);