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How can you remove a class name and replace it with a new one?

<style>
    .red {background-color: #FF0000;}
    .green{background-color: #00FF00;}
    .blue {background-color: #0000FF;}
</style>

<body class="red">
    <ul>
        <li><a href="">red</a></li>
        <li><a href="">green</a></li>
        <li><a href="">blue</a></li>
    </ul>
</body>

In this case when you click on red or green or blue, the body class name will change accordingly. Also it will make a cookie which will save the choice.

I tried the jQuery .addClass and it's working, but it's adding a class on top of the existing one. Also I can't manage to save the cookie.

How can you remove a class name and replace it with a new one?

<style>
    .red {background-color: #FF0000;}
    .green{background-color: #00FF00;}
    .blue {background-color: #0000FF;}
</style>

<body class="red">
    <ul>
        <li><a href="">red</a></li>
        <li><a href="">green</a></li>
        <li><a href="">blue</a></li>
    </ul>
</body>

In this case when you click on red or green or blue, the body class name will change accordingly. Also it will make a cookie which will save the choice.

I tried the jQuery .addClass and it's working, but it's adding a class on top of the existing one. Also I can't manage to save the cookie.

  • javascript
  • jquery
  • css
  • cookies
Share Improve this question edited Jan 8, 2018 at 13:13 Peter Mortensen 31.6k22 gold badges109 silver badges133 bronze badges asked Apr 29, 2009 at 22:37 kakkalokakkalo 8253 gold badges8 silver badges11 bronze badges 0
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3 Answers 3

Reset to default 18

Use:

$('.red').removeClass('red').addClass('blue');

Here's the full working code:

$(function() {
    $("a").click(function() {
        var color = $(this).text();
        $("body").removeClass().addClass(color);
        return false;
    });
});

And now for the cookie part

$(function() {
    $("a").click(function() {
        var color = $(this).text();
        $("body").removeClass().addClass(color);
        createCookie("color",color);
        return false;
    });

    if (readCookie("color") != null) {
      $("body").removeClass().addClass(readCookie("color"));

    }
    else {
      $("body").removeClass().addClass("red");
    }
});

function createCookie(name,value,days) {
    if (days) {
        var date = new Date();
        date.setTime(date.getTime()+(days*24*60*60*1000));
        var expires = "; expires="+date.toGMTString();
    }
    else
        var expires = "";
        document.cookie = name+"="+value+expires+"; path=/";
    }

    function readCookie(name) {
        var nameEQ = name + "=";
        var ca = document.cookie.split(';');
        for (var i=0;i < ca.length;i++) {
            var c = ca[i];
            while (c.charAt(0)==' ')
                c = c.substring(1,c.length);
            if (c.indexOf(nameEQ) == 0)
                return c.substring(nameEQ.length,c.length);
        }
        return null;
    }

    function eraseCookie(name) {
    createCookie(name,"",-1);
}

Working example here. A thank you to QuirksMode for the pre-made cookie code (cookie-cutter cookie code?)

Without jQuery you can do this with a line as simple as:

document.getElementsByTagName("body")[0].className = "red";

This effectively removes the class assigned to the element and replace it with whatever you want.

For cookies, PPK has a few simple methods to read/write/erase cookies.

createCookie("mySiteCookie", "red", 7); // Set the cookie to expire in 7 days.
readCookie("mySiteCookie"); // Should yield "red"

You'll also need removeClass.

本文标签： javascriptHow do I remove an existing class name and add a new one with jQuery and cookiesStack Overflow

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