Ionic using ref attr in span tag html

I have using some javascript in html page in the ionic3 project.

<span id="time" ref="{{product.time}}"></span>

But when build the project have error below:

Can't bind to 'ref' since it isn't a known property of 'span'.

Does anyone know how to solve this? Thanks a lot.

<span id="time" [attr.ref]="product.time"></span>