z-index

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The z-index CSS property specifies the stack level of the box in the current stacking context and whether the box establishes a local stacking context.

z-index: value;

object.style.zIndex = "value";

<'z-index'> = auto | <integer> | inherit

auto

Automatically specified by the user agent.

<integer>

Specifies one or more decimal digits (0-9).

inherit

Specifies the same value as the parent.

auto

<!doctype html>
<html>
<head>
    <style>
        img {
            position: absolute;
        }
        img:nth-of-type(1) {
            background-color: red;
        }
        img:nth-of-type(2) {
            background-color: green;
            left: 40px;
        }
        img:nth-of-type(3) {
            background-color: blue;
            left: 80px;
        }
    </style>
    <script>
        function mouseover(value) {
            var elements = document.getElementsByTagName("img");
            for (var i = 0; i < elements.length; ++i) {
                elements[i].style.zIndex = value;
                if (value == "integer") {
                    elements[i].style.zIndex = elements.length - i;
                }
            }
        }
    </script>
</head>
<body>
    <input onmouseover="mouseover(value)" type="button" value="auto">
    <input onmouseover="mouseover(value)" type="button" value="integer"><br>
    <img alt="Happy Face" src="/assets/png/HappyFace.png">
    <img alt="Happy Face" src="/assets/png/HappyFace.png">
    <img alt="Happy Face" src="/assets/png/HappyFace.png">
</body>
</html>

World Wide Web Consortium (W3C)

Syntax

CSS

JS

Values

Initial

Examples

auto

integer

JS

Links