A custom utility for classnames

clsx.ts

/**
 * Concatenate the specified classNames automatically with spaces.
 *  - If the className is undefined, it is ignored.
 *  - If the className is passed as a record of {class: condition }, it returns the class only if the condition is true.
 *
 * @example
 *      clsx('class1', 'class2', { class: true }) // 'class1 class2 class'
 *      clsx('class1', 'class2', { class: false }) // 'class1 class2'
 *      clsx('class1', undefined) // 'class1'
 *
 * @param args
 * @returns
 */
export function clsx(
    ...args: (string | undefined | Record<string, boolean>)[]
): string {
    const classes: string[] = [];

    for (const arg of args) {
        switch (typeof arg) {
            case 'string':
                classes.push(arg);
                break;
            case 'object':
                for (const key in arg) {
                    if (arg[key]) {
                        classes.push(key);
                    }
                }
                break;
        }
    }

    return classes.join(' ');
}