防抖函数

// 防抖
            _debounce(fn, dur = 200) {
                const context = this;
                let timer = null;
                return function (...args) {
                    if (timer) {
                        clearTimeout(timer)
                    }
                    timer = setTimeout(() => {
                        fn.apply(context, args)
                    }, dur)
                }
            },