JavaScript if...else if: Order Thresholds and Test Boundaries

The task

Classify nonnegative integer task durations as short below fifteen minutes, standard below forty-five, and extended otherwise. Use a separate ternary only to create a compact label from an already known Boolean.

Runnable Node 22 example

const assert = require('node:assert/strict');

function band(minutes) {
  if (!Number.isInteger(minutes) || minutes < 0) throw new RangeError('duration');
  if (minutes < 15) return 'short';
  else if (minutes < 45) return 'standard';
  else return 'extended';
}
assert.equal(band(14), 'short');
assert.equal(band(15), 'standard');
assert.equal(band(44), 'standard');
assert.equal(band(45), 'extended');
assert.throws(() => band(-1), RangeError);
const ready = true;
assert.equal(ready ? 'go' : 'wait', 'go');
console.log([14, 15, 44, 45].map(band).join(','));

Expected output and explanation

Fifteen belongs to standard because the first test is strictly below fifteen. Forty-five reaches extended for the same reason. The second branch does not need to restate the lower bound: reaching it means the earlier condition already failed.

The ternary produces one value from a Boolean choice. It does not replace every multi-branch workflow, especially when nested conditions make the rule harder to read. This tutorial groups that compact expression with conditional reasoning rather than creating another page for the same classification.

Pitfall to check

Putting the below-forty-five condition first would swallow short durations unless the branches were redesigned. Also validate the input before classification; otherwise a nonsensical value can fall through to a legitimate-looking category.