Ask for advice on a way to write in the element source code

when I look at the elementui source code, I find such a code :

const uploadComponent = <upload {...uploadData}>{trigger}</upload>;
return (
  <div>
    { this.listType === "picture-card" ? uploadList : ""}
    {
      this.$slots.trigger
        ? [uploadComponent, this.$slots.default]
        : uploadComponent
    }
    {this.$slots.tip}
    { this.listType !== "picture-card" ? uploadList : ""}
  </div>
);

Why is it possible to directly assign the js variable to a component structure here? Can the following structure be used as a return value for
?
would you like to know something about this way of writing? Is this js grammar or vue syntax?

Sep.22,2021

this is the jsx syntax

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