export type TSetCSSVarArgs = Parameters<typeof setCSSVar>;
export type TSetCSSVarReturn = ReturnType<typeof setCSSVar>;
/**
 * Sets CSS3 variable to specific DOM node
 * @param el{HTMLElement=} DOM element
 * @param variable{string} variable name
 * @param value{string|number|boolean=} variable value
 * @see https://developer.mozilla.org/en-US/docs/Web/CSS/Using_CSS_custom_properties
 * @returns {void}
 * @throws {TypeError} setCSSVar: el must be an HTMLElement
 * @throws {TypeError} setCSSVar: variable must be a non-empty string
 * @throws {TypeError} setCSSVar: value must be a string|number|boolean
 * @example
 * // How to set CSS variable to div?
 * // <div id="myBlock"></div>
 * const block = document.getElementById("myBlock");
 * setCSSVar(block, "myVar", 10);
 * // <div id="myBlock" style="--myVar: 10"></div>
 * @example
 * // Update a CSS progress variable from JavaScript
 * setCSSVar(progressBar, "progress", `${completedPercent}%`);
 */
export declare const setCSSVar: (el: HTMLElement | undefined, variable: string, value?: string | number | boolean) => void;