1.子组件被引用时，父组件如果以某一变量为子组件属性赋值，子组件需要根据赋值变换进而变化需要使用 name=“change” 的 handler

<!--parent-->
<aura:component>
    <aura:attribute name="a" type="String"/>
    <c:child childAttr="{!v.a}"/>
</aura:component>
<!--child-->
<aura:component>
    <aura:attribute name="childAttr" type="String"/>
    <aura:handler name="change" value="{!v.childAttr}" action="{!c.showAttr}"/>
    <!--Do not use name="init"-->
</aura:component>
<script>
    // child controller
    ({
        showAttr:function (cmp, event, helper) {
            console.log(cmp.get('v.childAttr'));// every time you changed childAttr, it shows.
        }
    })
</script>

2.当lightning中使用input标签type=“date”时，若要指定默认值需要默认固定格式的字符串，如：

<aura:component>
    <aura:attribute name="today" type="Date"/>
    <aura:handler action="{!c.init}" value="{!this}" name="init"/>
    <lightning:input label="Date" name="date" value="{!v.today}"/> <!--show today date-->
    <lightning:input label="Date" name="date" value="{!'2018-8-15'}"/>
</aura:component>
<script>
    // controller
    ({
        init:function (cmp, event, helper) {
            var today = new Date((new Date().getTime()));
            var monthDigit = today.getMonth() + 1;
            if (monthDigit <= 9) {
                monthDigit = '0' + monthDigit;
            }
            component.set('v.deadLine', today.getFullYear() + "-" + monthDigit + "-" + today.getDate());
        }
    })
</script>