Uncaught ReferenceError:menutoggle คือไม่กำหนดไว้ที่ HTMLImageElement.onclick

Uncaught ReferenceError:ฟังก์ชันคือไม่กำหนดไว้ที่ HTMLUnknownElement.onclick

//Your program can't find the function so do this.

//You can assign the button onclick as an id.
//then attach an eventListener on run time like this:

<button id="btn">Click me!</button>

var btn = document.getElementById("btn");
btn.addEventListener("click", function() {
	//Do something here
}, false);