利用节流+css动画优化窗口拖动onmousemove事件

本文需要实现点击拖动元素时，元素在指定元素窗口内拖动，不能超出窗口，并且做节流优化避免事件触发太多次导致的性能问题，css动画使元素移动更流畅，上代码

 

我们的元素

样式

#moveBox{
    z-index: 9999;
    top: 100px;
    left: 100px;
    position: fixed;
    width: 320px;
    height: 460px;
    background: #ffffff;
    box-shadow: 0px 8px 30px 0px rgba(0, 44, 102, 0.2);
    border-radius: 4px;
    transition-property: left , top;
    transition-duration: .2s , .2s;
}

准备一个节流函数

function throttle(func, delay = 100) {
	let timer = null,
		startTime = Date.now();

	return function() {
		let curTime = Date.now(),
			remaining = delay - (curTime - startTime),
			context = this,
			args = arguments;

		clearTimeout(timer);

		if (remaining <= 0) {
			func.apply(context, args);
			startTime = Date.now();
		} else {
			timer = setTimeout(func, remaining);
		}
	}
}

 

vue js部分代码

export default {
    data() {
        return {
            position: {
                left: '100px',
                top: '100px'
            }
        };
    },

    methods: {
        handleMouseDown(e) {
            let odiv = document.getElementById('moveBox'),
                appDiv = document.getElementById('app'),
                disX = e.clientX - odiv.offsetLeft, // 算出鼠标相对元素的位置
                disY = e.clientY - odiv.offsetTop;

            const throttleMove = throttle(event => {
                if (!event) return;

                // 鼠标按下并移动的事件
                // 用鼠标的位置减去鼠标相对元素的位置，得到元素的位置
                // 移动当前元素
                let left = event.clientX - disX,
                    top = event.clientY - disY,
                    widthThreshold = appDiv.offsetWidth - odiv.offsetWidth,
                    heightThreshold = appDiv.offsetHeight - odiv.offsetHeight;

                    
                if (left < 0) {
                    left = 0;  
                } else if (left > widthThreshold) { 
                    left = widthThreshold; 
                }

                if (top < 0) {
                    top = 0; 
                } else if(top > heightThreshold) { 
                    top = heightThreshold; 
                }

                this.position.left = left + 'px';
                this.position.top = top + 'px';
            }, 100);

            document.onmousemove = throttleMove;
            document.onmouseup = _ => {
                document.onmousemove = null;
                document.onmouseup = null;
            };
        }
    }
}

 

这样实现的效果，拖动元素时不会出现一卡一卡的效果，比较流畅，并且每秒触发的事件会很少性能上会有很大的提升