conditionalstyle

Conditionalstyle is a general term used to describe techniques for applying or altering visual styles based on conditions. It is not a single language feature but a pattern employed across stylesheets, scripting, and design systems to adapt presentation to state, data, environment, or user preferences.

In CSS, conditional styling relies on selectors, media queries, and feature queries. For example, using media queries like @media (max-width: 600px) to adjust layout, or pseudo-classes such as :hover or :focus to reflect interaction. CSS variables can be adjusted with JavaScript to implement conditional themes. There is no native conditional 'if' statement in CSS; instead, conditions are expressed through selectors and queries, and combined with the cascade.

In JavaScript and front-end frameworks, conditional styling is achieved by applying classes or inline styles based on runtime state. Examples: in plain JS, element.classList.add('hidden') when a condition is true; in React, className={condition ? 'active' : ''}; in Vue, :class="{'active': condition}". Frameworks often support binding to CSS variables for dynamic themes.

In data visualization and dashboards, conditional styling is used for data-driven coloring and formatting, often referred to as conditional formatting. Thresholds determine colors, stroke widths, or visibility; accessible color ramps and contrast considerations are important.

See also: conditional rendering, dynamic styling, theming, responsive design, feature detection.