message: fix: work around IE/Edge bug when accessing document.activeElement from iframe
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diff: @@ -63,7 +63,11 @@ function shouldUpdateValue (
  function isDirty (elm: acceptValueElm, checkVal: string): boolean {
  // return true when textbox (.number and .trim) loses focus and its value is
  // not equal to the updated value
  - return document.activeElement !== elm && elm.value !== checkVal
  + let notInFocus = true
  + // #6157
  + // work around IE bug when accessing document.activeElement in an iframe
  + try { notInFocus = document.activeElement !== elm } catch (e) {}
  + return notInFocus && elm.value !== checkVal
  }
  function isInputChanged (elm: any, newVal: string): boolean {
  