You should rather use the attribute placeholder to give the default value to the text input field. e.g. <input type="text" size="32" ... ... <看更多>

You can set the initial value of the state to the default value you want in a controlled component. If defaultValue was allowed, then it would ... ... <看更多>

You can set the initial value of the state to the default value you want in a controlled component. If defaultValue was allowed, then it would ... ... <看更多>

According to SF documentation, it is possible to be done without placeholder, just put default value in value field: <lightning:input ... ... <看更多>

This video will show you , how to get the old value of an input field , after it changed to new value . ... <看更多>