What does it mean if I can render to a floating point texture, but I'm told it's not supported?

Question

When I try to do the following, an alert box says "no".

var ext = gl.getExtension("OES_texture_float");
if (!ext) {
     alert("no");   
}

OES_texture_float also does not appear in my list of supported extensions.

Based off of this article , I then tried to determine if I can render to floating point textures.

var texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, 0,gl.RGBA, 2, 2, 0, gl.RGBA, gl.FLOAT, null);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);

var framebuffer = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);

var check = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
if(check != gl.FRAMEBUFFER_COMPLETE){
    alert("yes");
}
else{
    alert("no");
}

I get the alert yes. What does it mean that the extension is not supported, but I can apparently still render those textures? What can I do with just the second ability?

Thank you!

Answer 1

Your check is backward. It should say

if (check === gl.FRAMEBUFFER_COMPLETE) {
  alert("yes");

Also you got an error you'd likely see in the JavaScript console

WebGL: INVALID_ENUM: texImage2D: invalid type