/* Set the width of the side navigation to 250px and the left margin of the page content to 250px and add a black background color to body */
function openNav() {
document.getElementById("mySidenav").style.width = "250px";
document.getElementById("main").style.marginLeft = "250px";
document.body.style.backgroundColor = "rgba(0,0,0,0.4)";
}

/* Set the width of the side navigation to 0 and the left margin of the page content to 0, and the background color of body to white */
function closeNav() {
document.getElementById("mySidenav").style.width = "0";
document.getElementById("main").style.marginLeft = "0";
document.body.style.backgroundColor = "white";
}

<span onclick="openNav()">open</span>
<span onclick="closeNav()">open</span>

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