Import
FXAAShader is an addon, and must be imported explicitly, see Installation#Addons.
import { FXAAShader } from 'three/addons/shaders/FXAAShader.js';
Properties
.FXAAShader : ShaderMaterial~Shader (inner, constant)
FXAA algorithm from NVIDIA, C# implementation by Jasper Flick, GLSL port by Dave Hoskins.
References: