javascript - Setting an Instance to null -

so i've read through javascript memory management , few other articles, understand there garbage collecting daemon runs on interval , auto-magically cleans up.

the problem have if set object instance null , run timeout check null after setting null instance still exists.

here problem using simple example:

class animal{  	constructor(name){  		this.name = name;	  	}  }  class cat extends animal{  	constructor(name,type){  		super(name);  		this.type = type;  	}	  	renderhtml(){  		console.log(`rendering html...`);  		//variable exists while block executing...  		let divelement = document.createelement('div');  		//this should reference....  		divelement.addeventlistener('click',this.testinstancelife.bind(this));  		divelement.innerhtml = this.name;  		document.body.appendchild(divelement);  		//remove dom interface....  		document.body.removechild(divelement);  		console.log(`there should 0 references instance, since divelement should removed after block execution..`);  	}  	testinstancelife(){  		console.log(this);  	}  }  //init  (()=>{  	document.addeventlistener('domcontentloaded',()=>{  		var cat = new cat('grumpy','tabby');  		cat.renderhtml();  		cat = null;  		console.log(`this object now: ${cat}`);  		console.log(`finished executing...`);  	});  })();

question: why async timeout , or instance method still have reference though set null before both executed?