Function js_sys::Atomics::exchange

pub fn exchange(
    typed_array: &JsValue,
    index: u32,
    value: i32,
) -> Result<i32, JsValue>

The static Atomics.exchange() method stores a given value at a given position in the array and returns the old value at that position. This atomic operation guarantees that no other write happens until the modified value is written back.

You should use exchange_bigint to operate on a BigInt64Array or a BigUint64Array.

MDN documentation