Function shouldUpdateValue

vue.js:10588–10594

(elm, checkVal)

    // 判断你是否更新value
    function shouldUpdateValue(elm, checkVal) {
        return (!elm.composing && (
            elm.tagName === 'OPTION' ||
            isNotInFocusAndDirty(elm, checkVal) ||
            isDirtyWithModifiers(elm, checkVal)
        ))
    }

    function isNotInFocusAndDirty(elm, checkVal) {
        // return true when textbox (.number and .trim) loses focus and its value is