Debounce

debounce.js

/*
 * @param {Function} func
 *   需要进行去抖的函数
 * @param {number} wait
 *   去抖的时间间隔
 * @param {boolean} [lead = false]
 *   是否要在开始执行
 * @returns {Function}
 *   返回一个去抖函数
 */
function debounce(func, wait, lead) {
    var tid, timestamp,
        that, args;

    function delayed(timeout) {
        tid && clearTimeout(tid);
        tid = setTimeout(function () {
            handler();
        }, timeout);
    }

    function now() {
        return Date.now ? Date.now() : new Date().getTime();
    }

    function handler() {
        return func.apply(that, args);
    }

    return function __debounced__() {
        args = arguments;
        that = this;

        if (lead) {
            if (!timestamp || (now() - timestamp) >= wait) {
                handler();
            }
            timestamp = now();
        } else {
            delayed(wait);
        }
    };
}