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Offset related concepts + drag modal box case

2022-07-03 20:25:00 【MyDreamingCode】

One 、 offset Relevant concepts

offsetLeft: Refers to the left offset of the parent element with positioning （ If none, then body Benchmarking ）

offsetTop: Refers to the offset above the parent element with positioning

offsetWidth： Self width + padding + border read-only

offsetHeight： Self height + padding + border read-only

demo： Calculate when the mouse clicks on the box , Distance from the box

var box = document.querySelector('.box');
box.addEventListener('click', function(e) {
    var x = e.pageX - this.offsetLeft;
    var y = e.pageY - this.offsetTop;
    console.log(x,y);
})

Two 、 Drag modal box

Icon ： First think about how to calculate the distance that the big box needs to move ：

1. When the mouse is pressed ： Mouse pageX - Big box offsetLeft -> The distance of the mouse in the big box （ It doesn't change after ）

2. When the mouse moves ： Mouse pageX - The distance of the mouse in the big box （ I asked before ）

3. When the mouse is released ： To remove move event

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }
        .bg {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-color: rgba(0, 0, 0, .2);
            display: none;
        }
        button,.close {
            cursor: pointer;
        }
        .login {
            position: fixed;
            top: 50%;
            left: 50%;
            transform: translate(-50%,-50%);
            width: 300px;
            padding: 20px 0;
            z-index: 1;
            text-align: center;
            background-color: #fff;
            display: none;
        }
        .close {
            position: absolute;
            top: 0;
            right: 0;
            width: 20px;
            height: 20px;
            line-height: 20px;
            font-size: 20px;
        }
        h2 {
            margin-bottom: 15px;
            cursor: move;
        }
    </style>
</head>
<body>
    <button> Click to pop up the login box </button>
    <div class="login">
        <span class="close">x</span>
        <h2> Sign in </h2>
         user name ：<input type="text" placeholder=" Please enter a user name "><br/>
         password ：<input type="password" name="" id="" placeholder=" Please input a password "><br/>
    </div>
    <div class="bg"></div>
    <script>
        var btn = document.querySelector('button');
        var login = document.querySelector('.login');
        var bg = document.querySelector('.bg');
        var close = document.querySelector('.close');
        var chooseArea = document.querySelector('h2');

        btn.addEventListener('click', function() {
            login.style.display = 'block';
            bg.style.display = 'block';
        })
        close.addEventListener('click', function() {
            login.style.display = 'none';
            bg.style.display = 'none';
        })
        chooseArea.addEventListener('mousedown', function(e) {
            var x = e.pageX - login.offsetLeft;
            var y = e.pageY - login.offsetTop;
            document.addEventListener('mousemove', fn); 
            function fn(e) {
                login.style.left = e.pageX - x + 'px';
                login.style.top = e.pageY - y + 'px';
            }
            document.addEventListener('mouseup', function() {
                document.removeEventListener('mousemove', fn);
            })
        })
    </script>
</body>
</html>

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本文为[MyDreamingCode]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/02/202202150009109683.html