Why is gl_FragDepthEXT undefined in my WebGL fragment shader?

Question

I'm trying to follow documentation at:
https://developer.mozilla.org/en-US/docs/Web/API/EXT_frag_depth.

I want to have a fragment shader calculate depth in a step toward creating something more interesting.

Here is the broken code:
https://code.sololearn.com/W8a159A1485a

Shader compilation errors show in the JavaScript console as:
shaders.js:9 Shader compiler log: ERROR: 0:4: 'GL_EXT_frag_depth' : extension is disabled

If the gl_FragDepthEXT is commented out along with the #version, a red triangle is drawn.

Is setting depth so weird now that a browser flag needs to be turned on that is defaulted to disabled? Is the error related to my call to gl.getExtension('EXT_frag_depth')?

Please identify the code changes so this code actually calculates the depth for each pixel in the triangle. I've looked at many articles on setting depth in a WebGL shader and OpenGL shader so please don't just point me at an article that I've already seen.

Answer 1

trying
console.log(this.gl.getExtension('EXT_frag_depth'))

gives null which means that frag_depth extension is unavailable on your device ..so we cant use it...

for getting fragment coordinate you can use gl_FragCoord which is a vec3
and use like this

gl_FragColor=vec4(1.0,1.0,gl_FragCoord.z,1.0);

for maybe depth testing !?

hope that helps out!