How to Determine the Actual Line-Height of a DIV in JavaScript?

Determining Actual Line-Height of a DIV in JavaScript

Many JavaScript developers often seek methods to determine the actual line-height of a DIV element, excluding the influence of CSS property. While style.lineHeight provides some information, it relies on the existence of a CSS rule.

Problem Statement

Given a DIV element without a CSS-defined line-height, the challenge lies in finding a JavaScript solution that accurately measures the actual line-height regardless of font properties. This ensures consistent results for elements with varying content length and line breaks.

Solution

The most reliable and effective approach involves leveraging the clientHeight property. By creating a temporary element with identical font and size properties as the target element, we can extract its clientHeight. This value represents the actual line-height, including any vertical margins or white space within the DIV.

Here's an example implementation:

function getLineHeight(el) {
    var temp = document.createElement(el.nodeName), ret;
    temp.setAttribute("style", "margin:0; padding:0; "
        + "font-family:" + (el.style.fontFamily || "inherit") + "; "
        + "font-size:" + (el.style.fontSize || "inherit"));
    temp.innerHTML = "A";

    el.parentNode.appendChild(temp);
    ret = temp.clientHeight;
    temp.parentNode.removeChild(temp);

    return ret;
}

By "cloning" the target element's properties, this function generates a temporary element and measures its clientHeight. This technique provides an accurate representation of the actual line-height, even in scenarios with complex content or missing CSS rules.

The above is the detailed content of How to Determine the Actual Line-Height of a DIV in JavaScript?. For more information, please follow other related articles on the PHP Chinese website!