How do I make an objective for a game that ends the game when it is met

I don’t know how to make an objective so please tell me and try to make it as simple as it can be to add in also if you could tell me how I would install it

That is “objective” dependent. Basically it is going to be an if statement run every frame. The condition will be a test of whether your objective has completed. You did not indicate what the object is, so no one could tell you how to test for it.

You are probably going to also define what you mean by game end. You could just remove your render loop function and it would just be frozen.

at the end of the objective part are you saying that I need to tell people what the object is for them to tell me how to do it?

No, I more or less said you need to right better questions in order to get help.

Put something around this maybe:

var complete = false; // set to true somewhere, either in scene.render, or in render function below

// cannot be an anonymous function when needed to be stopped
function render() {
    // maybe check here if done, when not determined inside of render loop
   const mesh = scene.getMeshByName('it');   
   complete = mesh && mesh.position.z === 42;

    // always run, even if complete, so there can be a last frame to indicate, game over    
   scene.render();

   if (complete) engine.stopRenderLoop(render);
}
engine.runRenderLoop(render);