export interface ThrottleOptions {
    immediate: boolean; // 是否立即执行
}

/**
 * 节流
 * @category Utils
 * @param wait
 * @param fn
 * @param immediate 是否立即执行
 */
export const throttle = (fn, wait: number, {
    immediate = false
}: ThrottleOptions) => {
    let timer;
    let firstInvoke = immediate;

    return function(this, ...args) {
        const next = () => {
            fn.apply(this, args);
            timer = null;
        };

        // 如果是第一次触发，直接执行
        if (firstInvoke) {
            firstInvoke = false;
            next();
        }

        if (!timer) {
            timer = setTimeout(() => {
                clearTimeout(timer);
                timer = null;
                fn.apply(this, args);
            }, wait);
        }
    };
};