Function shouldUpdateValue

static/vuejs/vue.runtime.common.js:5514–5524

(
  elm,
  vnode,
  checkVal
)

function shouldUpdateValue (
  elm,
  vnode,
  checkVal
) {
  return (!elm.composing && (
    vnode.tag === 'option' ||
    isDirty(elm, checkVal) ||
    isInputChanged(elm, checkVal)
  ))
}

function isDirty (elm, checkVal) {
  // return true when textbox (.number and .trim) loses focus and its value is not equal to the updated value