多分可読でポリゴン描く30行以下のWebGLコード。

shortwebgl.html

<canvas id="CNVS" width="512px" height="512px"></canvas>
<script>
const vsrc="attribute vec4 p;void main(){gl_Position=vec4(p.xy*.9,0.,1.);}";
const fsrc="void main(){gl_FragColor=vec4(1);}";
const gl=document.getElementById("CNVS").getContext("webgl");
enableStaticAttr2f(gl,0, new Float32Array([-1,-1,-1,1,1,-1,1,1]));
var prg,vs,fs;
vs=gl.createShader(gl.VERTEX_SHADER);	setSource(vs,vsrc);	log(compile(vs));
fs=gl.createShader(gl.FRAGMENT_SHADER);	setSource(fs,fsrc);	log(compile(fs));
prg=gl.createProgram();	attach(prg,vs);	attach(prg,fs);	log(link(prg));
gl.useProgram(prg);
gl.clearColor(0,.5,0,1);	gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
function attach(p, s){gl.attachShader(p,s);}
function setSource(s,src){gl.shaderSource(s,src);}
function compile(s){gl.compileShader(s);return gl.getShaderInfoLog(s);}
function link(p){gl.linkProgram(p);return gl.getProgramInfoLog(p);}
function enableStaticAttr2f(gl, attr, data){
	var buf=gl.createBuffer();
	gl.bindBuffer(gl.ARRAY_BUFFER,buf);
	gl.enableVertexAttribArray(attr);
	gl.vertexAttribPointer(attr, 2, gl.FLOAT, false,0,0);
	gl.bufferData(gl.ARRAY_BUFFER, data, gl.STATIC_DRAW)
}
function log(str){console.log(str);}
</script>