Note: This feature is available in Web Workers.
The read-only WebGLRenderingContext.drawingBufferHeight property represents the actual height of the current drawing buffer. It should match the height attribute of the <canvas> element associated with this context, but might differ if the implementation is not able to provide the requested height.
A number.
Given this <canvas> element:
<canvas id="canvas"></canvas>You can get the height of the drawing buffer with the following lines:
const canvas = document.getElementById("canvas");
const gl = canvas.getContext("webgl");
gl.drawingBufferHeight; // 150