2021.8.10今日小结

2024-03-07 20:10:27

今天学习了几个基本的事件问题，鼠标滚轮事件,用键盘控制div移动，键盘事件，比如可以禁用从键盘输入时，输入框不接受某些数字或者字母。拖拽div，定时器。

鼠标滚轮事件

//鼠标滚轮事件
<style>
        #box1{
            width: 100px;
            height: 100px;
            background-color: red;
        }
        body{
            height: 2000px;
        }
    </style>
    <script>
        window.onload = function(){
            let box1 = document.getElementById("box1");

                box1.onmousewheel = function(event){
                    event = event || window.event;
                    
                    if(event.wheelDelta>0 || event.detail<0){
                        box1.style.height = box1.clientHeight - 10 +"px";
                    }else{
                        box1.style.height = box1.clientHeight + 10 +"px";
                    }
                    event.preventDefault && event.preventDefault();
                    return false;
                };
                bind(box1,"DOMMouseScroll",box1.onmousewheel);
            
        };
        function bind(obj ,eventStr , callback){
            if(obj.addEventListener){
                // 大部分浏览器的兼容方式
                obj.addEventListener(eventStr , callback ,false);
            }else{
                // this是谁由调用方式决定

                // IE8及以下
                obj.addEventListener("on"+eventStr,function(){
                    callback.call(obj);
                });
            }
        };
    </script>
</head>
<body>
    <div id="box1"></div> 
</body>

用键盘控制div移动

//用键盘控制div移动   
 <style>
        #box1{
            width: 100px;
            height: 100px;
            background-color: red;
            position: absolute;
        }
    </style>
    <script>
        window.onload = function(){
            document.onkeydown =function(event){
                event = event || window.event;

                let speed =10;
                if(event.ctrlKey){
                    speed = 50;
                }

                //37左38上39右40下

                switch(event.keyCode){
                    case 37:
                        box1.style.left = box1.offsetLeft -speed +"px";
                        break;
                    case 38:
                        box1.style.top = box1.offsetTop -speed +"px";
                        break;
                    case 39:
                        box1.style.left = box1.offsetLeft +speed +"px";
                        break;
                    case 40:
                        box1.style.top = box1.offsetTop +speed +"px";
                        break;
                }
            };
        };
    </script>
</head>
<body>
    <div id="box1"></div>
</body>

键盘事件

<script>
        window.onload = function(){
            

            document.onkeydown = function(){
                event = event || window.event;

                if(event.keyCode === 89 && event.ctrlKey){
                    console.log("ctrl和y都被按下");
                }
            };
            // document.onkeyup = function(){
                
            // };


            let input = document.getElementsByTagName("input")[0];
            input.onkeydown = function(event){
                event = event || window.event;
                if(event.keyCode>=48 && event.keyCode<=57){
                    return false;
                }
            };
        };
    </script>
</head>
<body>
    <input type="text">
</body>

div拖拽

<style>
        #box1{
            height: 100px;
            width: 100px;
            background-color: red;
            position: absolute;
        }
        #box2{
            height: 100px;
            width: 100px;
            background-color: yellow;
            position: absolute;
            top: 100px;
            left: 100px;
        }
    </style>
    <script>
        window.onload = function(){
            let box1 = document.getElementById("box1");
            
            drag(box1);

            drag(box2);
            
            //提取一个专门用来拖拽的函数
            function drag(obj){
                obj.onmousedown = function(event){

                    event = event || window.event;

                        let ol = event.clientX - obj.offsetLeft;
                        let ot = event.clientY - obj.offsetTop;



                            document.onmousemove = function(event){
                                event = event || window.event;

                                let left = event.clientX-ol;
                                let top = event.clientY-ot;

                                obj.style.left = left + "px";
                                obj.style.top = top +"px";
                            };
                            document.onmouseup = function(){
                                document.onmousemove = null;
                                document.onmouseup = null;
                            };
                            //取消默认行为
                            return false;
                            };
                    };
        };
    </script>
</head>
<body>
    <div id="box1"></div>
    <div id="box2"></div>
</body>

定时器，比如图片轮播图时候就可以使用。


 setInterval(function(){
　　　　　　　　　　
                index++;
　　　　　　　　　　//如果index计数器大于了图片数量将重新开始
                if(index>=imgArr.length){
                    index=0;
                }

                img.src = imgArr[index];
            },2000);//时间两秒钟一次

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