Custom content does not work

[huangjinlei666]

I want to customize the content, but the generated watermark content is undefined

The code is as follows

OptionConfig : { mode: "bottomleft", textBaseline: "middle", font: "12px Arial", fillStyle: "white", content: ${this.now}, rotate: 45 }

//username,userid from data computed: { now(){ return this.username+this.userid+dayjs().format("YYYY-MM-DD HH:mm:ss") } },