vue/src/platforms/web/runtime/modules/dom-props.js

/* @flow */

import { isDef, isUndef, extend, toNumber } from 'shared/util'

function updateDOMProps (oldVnode: VNodeWithData, vnode: VNodeWithData) {
  if (isUndef(oldVnode.data.domProps) && isUndef(vnode.data.domProps)) {
    return
  }
  let key, cur
  const elm: any = vnode.elm
  const oldProps = oldVnode.data.domProps || {}
  let props = vnode.data.domProps || {}
  // clone observed objects, as the user probably wants to mutate it
  if (isDef(props.__ob__)) {
    props = vnode.data.domProps = extend({}, props)
  }

  for (key in oldProps) {
    if (isUndef(props[key])) {
      elm[key] = ''
    }
  }
  for (key in props) {
    cur = props[key]
    // ignore children if the node has textContent or innerHTML,
    // as these will throw away existing DOM nodes and cause removal errors
    // on subsequent patches (#3360)
    if (key === 'textContent' || key === 'innerHTML') {
      if (vnode.children) vnode.children.length = 0
      if (cur === oldProps[key]) continue
    }

    if (key === 'value') {
      // store value as _value as well since
      // non-string values will be stringified
      elm._value = cur
      // avoid resetting cursor position when value is the same
      const strCur = isUndef(cur) ? '' : String(cur)
      if (shouldUpdateValue(elm, vnode, strCur)) {
        elm.value = strCur
      }
    } else {
      elm[key] = cur
    }
  }
}

// check platforms/web/util/attrs.js acceptValue
type acceptValueElm = HTMLInputElement | HTMLSelectElement | HTMLOptionElement;

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

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
  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 {
  const value = elm.value
  const modifiers = elm._vModifiers // injected by v-model runtime
  if (isDef(modifiers) && modifiers.number) {
    return toNumber(value) !== toNumber(newVal)
  }
  if (isDef(modifiers) && modifiers.trim) {
    return value.trim() !== newVal.trim()
  }
  return value !== newVal
}

export default {
  create: updateDOMProps,
  update: updateDOMProps
}