code: function AtomicsCompareExchangeJS(sta, index, oldValue, newValue) {
    CheckSharedIntegerTypedArray(sta);
    index = ValidateIndex(index, %_TypedArrayGetLength(sta));
    oldValue = TO_NUMBER(oldValue);
    newValue = TO_NUMBER(newValue);
    return %_AtomicsCompareExchange(sta, index, oldValue, newValue);
  }
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