如何转换此代码以便函数可以采用变量？

Question

I am trying to change the color of nav bar elements when the mouse goes over them.

This piece of code does that but for only the first button:

let navOne = document.getElementById("nav1");

function mouseOn() {
    nav1.style.color = "red";
}

function mouseOff() {
    nav1.style.color = "black";
}

navOne.addEventListener('mouseover', mouseOn);
navOne.addEventListener('mouseout', mouseOff);

I have been trying to convert the code so the functions work for multiple buttons, but cannot seem to get it to work. Here is the code so far:

let navOne = document.getElementById("nav1");

function mouseOn(navButton) {
    navButton.style.color = "red";
}

function mouseOff(navButton) {
    navButton.style.color = "black";
}

navOne.addEventListener('mouseover', mouseOn(navOne));
navOne.addEventListener('mouseout', mouseOff(navOne));

It has no errors, but does not cause any color change when I move my mouse button over the nav1 element.

Any help is greatly appreciated.

Answer 1

You can have the event handler functions take advantage of the event parameter that is passed in:

 function mouseOn(e) { e.target.style.color = "red"; } function mouseOff(e) { e.target.style.color = "black"; } for (let navItem of document.querySelectorAll('nav a')) { navItem.addEventListener('mouseover', mouseOn); navItem.addEventListener('mouseout', mouseOff); }

 nav a { display: inline-block; padding: 10px; color: black; }

 <nav> <a href="#" id="nav1">Nav One</a> <a href="#" id="nav2">Nav Two</a> </nav>

However, using a css :hover pseudo-attribute would be the preferred approach nowadays. No JS code needed.

 nav a { display: inline-block; padding: 10px; color: black; } nav a:hover { color: red; }

 <nav> <a href="#">Nav One</a> <a href="#">Nav Two</a> </nav>