Detect mouse position and trigger function

Question

The idea is that x-coordinate of the mouse be tracked so when it goes within a certain threshold(250px) in this case to the left edge of the window it triggers the function "openNav", and closes it when the mouse leaves the 250px threshold.

I read a few forums and posts but can't seem to find much on how to use the ClientX function.The code below is just what I think how it should work, but it obviously doesn't. I would be delighted if anyone could give me some sort of idea or even example on how to execute the above.

Thank you in advance.

function openNav() {
  document.getElementById("mySidenav").style.width = "250px";
  document.getElementById("main").style.marginLeft = "250px";
}

function closeNav() {
  document.getElementById("mySidenav").style.width = "0";
  document.getElementById("main").style.marginLeft = "0";
}

var x = e.clientX;
for (x - 250 <= 0) {
  openNav()
}

body {
  font-family: "Lato", sans-serif;
}

.sidenav {
  height: 100%;
  width: 0;
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  background-color: #111;
  overflow-x: hidden;
  transition: 0.5s;
  padding-top: 60px;
}

.sidenav a {
  padding: 8px 8px 8px 32px;
  text-decoration: none;
  font-size: 25px;
  color: #818181;
  display: block;
  transition: 0.3s;
}

.sidenav a:hover {
  color: #f1f1f1;
}

.sidenav .closebtn {
  position: absolute;
  top: 0;
  right: 25px;
  font-size: 36px;
  margin-left: 50px;
}

#main {
  transition: margin-left .5s;
  padding: 16px;
}

@media screen and (max-height: 450px) {
  .sidenav {
    padding-top: 15px;
  }
  .sidenav a {
    font-size: 18px;
  }
}

<div id="mySidenav" class="sidenav">
  <a href="javascript:void(0)" class="closebtn" onclick="closeNav()">&times;</a>
  <a href="#">1</a>
  <a href="#">2</a>
  <a href="#">3</a>
  <a href="#">4</a>
</div>

<div>
  <button class="button open" onclick="openNav()">OPEN</button>
</div>
<div id="main">
  <h2>Courses</h2>
</div>

Answer 1

clientX is not a function but a property of the mouse event.

Just observe the mousemove event and trigger your function according to event.clientX.

function openNav() {
  document.getElementById("mySidenav").style.width = "250px";
  document.getElementById("main").style.marginLeft = "250px";
}

function closeNav() {
  document.getElementById("mySidenav").style.width = "0";
  document.getElementById("main").style.marginLeft = "0";
}

document.addEventListener('mousemove', function(event) {
  console.log(event.clientX);
  if (event.clientX < 250) {
    openNav();
  } else {
    closeNav();
  }
})

body {
  font-family: "Lato", sans-serif;
}

.sidenav {
  height: 100%;
  width: 0;
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  background-color: #111;
  overflow-x: hidden;
  transition: 0.5s;
  padding-top: 60px;
}

.sidenav a {
  padding: 8px 8px 8px 32px;
  text-decoration: none;
  font-size: 25px;
  color: #818181;
  display: block;
  transition: 0.3s;
}

.sidenav a:hover {
  color: #f1f1f1;
}

.sidenav .closebtn {
  position: absolute;
  top: 0;
  right: 25px;
  font-size: 36px;
  margin-left: 50px;
}

#main {
  transition: margin-left .5s;
  padding: 16px;
}

@media screen and (max-height: 450px) {
  .sidenav {
    padding-top: 15px;
  }
  .sidenav a {
    font-size: 18px;
  }
}

<div id="mySidenav" class="sidenav">
  <a href="javascript:void(0)" class="closebtn" onclick="closeNav()">&times;</a>
  <a href="#">1</a>
  <a href="#">2</a>
  <a href="#">3</a>
  <a href="#">4</a>
</div>

<div>
  <button class="button open" onclick="openNav()">OPEN</button>
</div>
<div id="main">
  <h2>Courses</h2>
</div>

In the above version the openNav() and closeNav() function will be uselessly called multiple times. You should have a flag that keeps track of the menu's state and only calls the appropriate function when needed.

Answer 2

Here is how you'll get the x-coordinates. You can trigger anyother function based on whatever condition

document.addEventListener("mousemove", function(e){
    document.getElementById("x").innerHTML = e.clientX
    if(e.clientX > 250){
      alert("Crossed")
    }
});
function openNav() {
    document.getElementById("mySidenav").style.width = "250px";
    document.getElementById("main").style.marginLeft = "250px";
}

function closeNav() {
    document.getElementById("mySidenav").style.width = "0";
    document.getElementById("main").style.marginLeft= "0";
}

<style>
body {
    font-family: "Lato", sans-serif;
}

.sidenav {
    height: 100%;
    width: 0;
    position: fixed;
    z-index: 1;
    top: 0;
    left: 0;
    background-color: #111;
    overflow-x: hidden;
    transition: 0.5s;
    padding-top: 60px;
}

.sidenav a {
    padding: 8px 8px 8px 32px;
    text-decoration: none;
    font-size: 25px;
    color: #818181;
    display: block;
    transition: 0.3s;
}

.sidenav a:hover {
    color: #f1f1f1;
}

.sidenav .closebtn {
    position: absolute;
    top: 0;
    right: 25px;
    font-size: 36px;
    margin-left: 50px;
}

#main {
    transition: margin-left .5s;
    padding: 16px;
}

@media screen and (max-height: 450px) {
  .sidenav {padding-top: 15px;}
  .sidenav a {font-size: 18px;}
}
</style>

<!DOCTYPE html>
<html>
<head>
</head>
<body>

<div id="mySidenav" class="sidenav">
  <a href="javascript:void(0)" class="closebtn" onclick="closeNav()">&times;</a>
  <a href="#">1</a>
  <a href="#">2</a>
  <a href="#">3</a>
  <a href="#">4</a>
</div>

<div>
	<button class="button open" onclick="openNav()">OPEN</button>
</div>
<div id="main">
  <h2>Courses <small id="x"></small></h2>
</div>

</body>
</html>

Answer 3

clientX is a property of a mouse event. You need to use it inside an event handler. So we just define en event handler for the entire document and:

document.addEventListener('mousemove', function(event) {
    event.clientX < 250 ? openNav() : closeNav();
});

Answer 4

just setup a div with the right size and position and then call your function on the mouse enter event

$('#myDiv').on("mouseenter", function (e) {
  //your code
});