HTML

click the button and change the button text

<input onclick="change()" type="button" value="Open Curtain" id="myButton1"></input>

html how to change button text

<input type="button" value="Button Text Here">

change the text value for a HTML element

const btn = document.getElementById("btn");

btn.addEventListener("click", ()=>{

    if(btn.innerText === "Red"){
        btn.innerText = "Blue";
    }else{
        btn.innerText= "Red";
    }
});