Template reference variables ( #var )

A template reference variable is often a reference to a DOM element
within a template. It can also be a reference to an Angular component
or directive or a web component.

所以,你只需要< div #var>,#var在此< div>上声明一个var变量元件.

In most cases,Angular sets the reference variable’s value to the
element on which it was declared…. But a directive can change that
behavior and set the value to something else,such as itself. The
NgForm directive does that

如果在模板引用变量中指定了某些内容,则它应该是指令或组件,例如：#var =“ngForm”,其中ngForm是内置指令.

这就是为什么你得到一个错误：没有指令“exportAs”设置为“#var”

因为#var(您指定的：< div #var =“#var”>)不是组件也不是指令,

现在对于jade(pug),如果你想要一个null属性,你应该设置编译器to compile to HTML doctype,因为pug的默认行为是设置属性上的属性值：

默认行为：

div(#var)编译为：< div #var =“#var”>< / div>

div(隐藏)编译为< div hidden =“hidden”>< / div>

使用doctype html：

div(#var)编译为：< div#var>< / div>

div(隐藏)编译为< div hidden>< / div>

或者你可以把文件的开头：doctype html放到你想要的每个文件中.