The length read-only property of the GPUCompilationMessage interface is a number representing the length of the substring that the message corresponds to.

A number.

To be precise, length is the number of UTF-16 code units in the shader code substring that the message corresponds to. If the message corresponds to a single point rather than a substring, length will be 0.

  // ...
  const shaderModule = device.createShaderModule({
    code: shaders,
  });

  const shaderInfo = await shaderModule.getCompilationInfo();
  const firstMessage = shaderInfo.messages[0];
  console.log(firstMessage.length);
  // ...
}

See the main GPUCompilationInfo page for a more detailed example.

• The WebGPU API