Function load 

pub fn load<T>(typed_array: &T, index: u32) -> Result<i32, JsValue>
where
    T: TypedArray + ErasableGenericBorrow<Int32Array>,

The static Atomics.load() method returns a value at a given position in the array.

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

MDN documentation