src/heapreplace.js

import {IndexError} from '@failure-abstraction/error';
import {siftdown} from './core/index.js';

export default function heapreplace(heap, item) {
	const x = heap.data;
	const n = x.length;

	if (n === 0) throw new IndexError('heapreplace');

	const oldroot = x[0];

	x[0] = item;

	// Sift down the new root

	siftdown(heap.compare, x, 0, n, 0);

	return oldroot;
}