Tag element

x^2 <katex>x^2</katex>

Attribute

x^2 <span katex>x^2</span>

Attribute value

<span katex="x^2"></span>

expr attribute value

<katex expr="x^2"></katex>

Bind to scope

<input ng-model="tex">
<katex bind="tex"></katex>

Display mode

<div katex="x^2" display-mode></div>

Don't show error

<div katex="\"
  on-error="$setText('')"
></div>

on-error locals:
  $expr: (string) expression
  $err: (object) error
  $setText: (function) set text

Auto-render

This uses the katex auto-render extension. 
<div katex auto-render>
  <b>Exponentiation</b>
  is written as \(b^n\)
</div>
Exponentiation is written as \(b^n\) 
<input ng-model="autoRenderTex">
<katex bind="autoRenderTex"
  auto-render></katex>