I got a simple JavaScript that changes the inner HTML of an element when links are clicked, it looks like this:

function changeHeader(Index)
{
    var headers = new Array("Coffee tables","Side tables","Stand tables","Dinner tables","Stools","Pedestals");
    document.getElementById("header").innerHTML = headers[Index];

}

The CSS for header is below:

#header
{
    cursor: hand; 
    cursor: pointer;
    -webkit-touch-callout: none;
    -webkit-user-select: none;
    -khtml-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}

And the HTML is basically this:

<p id="header">Press a link</p>
<a href=# onclick="changeHeader(1)">Coffee tables</a>
<a href=# onclick="changeHeader(2)">Side tables</a>
<a href=# onclick="changeHeader(3)">Stand tables</a>

And so on. My problem is that I'd like to have different background colors on the header element depending on what link is pressed. The first link might get a red background, the second a blue, the third a green and so on..

How can I use JavaScript to add a property to an already existing CSS id? I don't use jQuery, so only pure JavaScript please :)

I got a simple JavaScript that changes the inner HTML of an element when links are clicked, it looks like this:

function changeHeader(Index)
{
    var headers = new Array("Coffee tables","Side tables","Stand tables","Dinner tables","Stools","Pedestals");
    document.getElementById("header").innerHTML = headers[Index];

}

The CSS for header is below:

#header
{
    cursor: hand; 
    cursor: pointer;
    -webkit-touch-callout: none;
    -webkit-user-select: none;
    -khtml-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}

And the HTML is basically this:

<p id="header">Press a link</p>
<a href=# onclick="changeHeader(1)">Coffee tables</a>
<a href=# onclick="changeHeader(2)">Side tables</a>
<a href=# onclick="changeHeader(3)">Stand tables</a>

And so on. My problem is that I'd like to have different background colors on the header element depending on what link is pressed. The first link might get a red background, the second a blue, the third a green and so on..

How can I use JavaScript to add a property to an already existing CSS id? I don't use jQuery, so only pure JavaScript please :)

• javascript
• css
• class

4 Answers 4

You could use style property

document.getElementById("header").style.backgroundColor = 'red';

You can change your approach a little:

function changeHeader(Index) {
    var headers = [
        {color: 'red', text: "Coffee tables"},
        {color: 'blue', text: "Side tables",
        {color: '#DDD', text: "Stand tables"},
        {color: "#ACD12A", text: "Dinner tables"},
        {color: "Chuck Norris", text: "Stools"}
    ];
    var header = document.getElementById("header"),
    header.innerHTML = headers[Index].text;
    header.style.backgroundColor = headers[Index].color;
}​

You don't need to add an additional property to the ID, either you add inline-styling to the element, or if you don't want to use inline-styling you add an additional class to the element instead, that sets the proper background color.

Here is an example of how you can add/remove classes from an element, without using jQuery: http://snipplr.com/view/3561/addclass-removeclass-hasclass/

See sample code in this page : http://jsfiddle.net/Rd4y5/

js :

d = document.getElementById("d1");
console.log(d.style);
d.style.backgroundColor="red";
d.style.width = "300px";
d.style.height="300px";
    console.log(d.style);

html :

<div id='d1'>a<div>​