【工作记录】基于CSS+JS可拖拽改变大小、可吸附到边界的DIV

记录一段实现可拖拽、可自动吸附到边界的代码。

<!DOCTYPE html>
<html lang="en">
<head>
    <style>
        body {
            overflow: hidden;
        }
        #pane {
            position: absolute;
            width: 45%;
            height: 45%;
            top: 20%;
            left: 20%;
            margin: 0;
            padding: 0;
            z-index: 99;
            border: 2px solid purple;
            background: #fefefe;
        }

        #title {
            font-family: monospace;
            background: purple;
            color: white;
            font-size: 16px;
            height: 22px;
            text-align: center;
        }

        #ghostpane {
            background: #999;
            opacity: 0.2;
            width: 45%;
            height: 45%;
            top: 20%;
            left: 20%;
            position: absolute;
            margin: 0;
            padding: 0;
            z-index: 98;
            -webkit-transition: all 0.25s ease-in-out;
            -moz-transition: all 0.25s ease-in-out;
            -ms-transition: all 0.25s ease-in-out;
            -o-transition: all 0.25s ease-in-out;
            transition: all 0.25s ease-in-out;
        }
    </style>
    <title>测试div可拖拽</title>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
</head>
<body>
<div>
    这里是测试文本
</div>
<div id="pane">
    <div id="title">属性配置</div>
</div>
<div id="ghostpane"></div>
<script>
    // Minimum resizable area
    var minWidth = 400;
    var minHeight = 200;

    // Thresholds
    var FULLSCREEN_MARGINS = -10;
    var MARGINS = 4;

    // End of what's configurable.
    var clicked = null;
    var onRightEdge, onBottomEdge, onLeftEdge, onTopEdge;

    var rightScreenEdge, bottomScreenEdge;

    var preSnapped;

    var b, x, y;

    var redraw = false;

    var pane = document.getElementById('pane');
    var ghostpane = document.getElementById('ghostpane');

    function setBounds(element, x, y, w, h) {
        element.style.left = x + 'px';
        element.style.top = y + 'px';
        element.style.width = w + 'px';
        element.style.height = h + 'px';
    }

    function hintHide() {
        setBounds(ghostpane, b.left, b.top, b.width, b.height);
        ghostpane.style.opacity = 0;
    }


    // Mouse events
    pane.addEventListener('mousedown', onMouseDown);
    document.addEventListener('mousemove', onMove);
    document.addEventListener('mouseup', onUp);

    // Touch events
    pane.addEventListener('touchstart', onTouchDown);
    document.addEventListener('touchmove', onTouchMove);
    document.addEventListener('touchend', onTouchEnd);


    function onTouchDown(e) {
        onDown(e.touches[0]);
        e.preventDefault();
    }

    function onTouchMove(e) {
        onMove(e.touches[0]);
    }

    function onTouchEnd(e) {
        if (e.touches.length === 0) onUp(e.changedTouches[0]);
    }

    function onMouseDown(e) {
        onDown(e);
        e.preventDefault();
    }

    function onDown(e) {
        calc(e);

        var isResizing = onRightEdge || onBottomEdge || onTopEdge || onLeftEdge;

        clicked = {
            x: x,
            y: y,
            cx: e.clientX,
            cy: e.clientY,
            w: b.width,
            h: b.height,
            isResizing: isResizing,
            isMoving: !isResizing && canMove(),
            onTopEdge: onTopEdge,
            onLeftEdge: onLeftEdge,
            onRightEdge: onRightEdge,
            onBottomEdge: onBottomEdge
        };
    }

    function canMove() {
        return x > 0 && x < b.width && y > 0 && y < b.height && y < 30;
    }

    function calc(e) {
        b = pane.getBoundingClientRect();
        x = e.clientX - b.left;
        y = e.clientY - b.top;

        onTopEdge = y < MARGINS;
        onLeftEdge = x < MARGINS;
        onRightEdge = x >= b.width - MARGINS;
        onBottomEdge = y >= b.height - MARGINS;

        rightScreenEdge = window.innerWidth - MARGINS;
        bottomScreenEdge = window.innerHeight - MARGINS;
    }

    let e;

    function onMove(ee) {
        calc(ee);

        e = ee;

        redraw = true;

    }

    function animate() {

        requestAnimationFrame(animate);

        if (!redraw) return;

        redraw = false;

        if (clicked && clicked.isResizing) {

            if (clicked.onRightEdge) pane.style.width = Math.max(x, minWidth) + 'px';
            if (clicked.onBottomEdge) pane.style.height = Math.max(y, minHeight) + 'px';

            if (clicked.onLeftEdge) {
                var currentWidth = Math.max(clicked.cx - e.clientX + clicked.w, minWidth);
                if (currentWidth > minWidth) {
                    pane.style.width = currentWidth + 'px';
                    pane.style.left = e.clientX + 'px';
                }
            }

            if (clicked.onTopEdge) {
                var currentHeight = Math.max(clicked.cy - e.clientY + clicked.h, minHeight);
                if (currentHeight > minHeight) {
                    pane.style.height = currentHeight + 'px';
                    pane.style.top = e.clientY + 'px';
                }
            }

            hintHide();

            return;
        }

        if (clicked && clicked.isMoving) {

            if (b.top < FULLSCREEN_MARGINS || b.left < FULLSCREEN_MARGINS || b.right > window.innerWidth - FULLSCREEN_MARGINS || b.bottom > window.innerHeight - FULLSCREEN_MARGINS) {
                // hintFull();
                setBounds(ghostpane, 0, 0, window.innerWidth, window.innerHeight);
                ghostpane.style.opacity = 0.2;
            } else if (b.top < MARGINS) {
                // hintTop();
                setBounds(ghostpane, 0, 0, window.innerWidth, window.innerHeight / 2);
                ghostpane.style.opacity = 0.2;
            } else if (b.left < MARGINS) {
                // hintLeft();
                setBounds(ghostpane, 0, 0, window.innerWidth / 2, window.innerHeight);
                ghostpane.style.opacity = 0.2;
            } else if (b.right > rightScreenEdge) {
                // hintRight();
                setBounds(ghostpane, window.innerWidth / 2, 0, window.innerWidth / 2, window.innerHeight);
                ghostpane.style.opacity = 0.2;
            } else if (b.bottom > bottomScreenEdge) {
                // hintBottom();
                setBounds(ghostpane, 0, window.innerHeight / 2, window.innerWidth, window.innerWidth / 2);
                ghostpane.style.opacity = 0.2;
            } else {
                hintHide();
            }

            if (preSnapped) {
                setBounds(pane,
                    e.clientX - preSnapped.width / 2,
                    e.clientY - Math.min(clicked.y, preSnapped.height),
                    preSnapped.width,
                    preSnapped.height
                );
                return;
            }

            // moving
            pane.style.top = (e.clientY - clicked.y) + 'px';
            pane.style.left = (e.clientX - clicked.x) + 'px';

            return;
        }

        // This code executes when mouse moves without clicking

        // style cursor
        if (onRightEdge && onBottomEdge || onLeftEdge && onTopEdge) {
            pane.style.cursor = 'nwse-resize';
        } else if (onRightEdge && onTopEdge || onBottomEdge && onLeftEdge) {
            pane.style.cursor = 'nesw-resize';
        } else if (onRightEdge || onLeftEdge) {
            pane.style.cursor = 'ew-resize';
        } else if (onBottomEdge || onTopEdge) {
            pane.style.cursor = 'ns-resize';
        } else if (canMove()) {
            pane.style.cursor = 'move';
        } else {
            pane.style.cursor = 'default';
        }
    }

    animate();

    function onUp(e) {
        calc(e);

        if (clicked && clicked.isMoving) {
            // Snap
            var snapped = {
                width: b.width,
                height: b.height
            };

            if (b.top < FULLSCREEN_MARGINS || b.left < FULLSCREEN_MARGINS || b.right > window.innerWidth - FULLSCREEN_MARGINS || b.bottom > window.innerHeight - FULLSCREEN_MARGINS) {
                // hintFull();
                setBounds(pane, 0, 0, window.innerWidth, window.innerHeight);
                preSnapped = snapped;
            } else if (b.top < MARGINS) {
                // hintTop();
                setBounds(pane, 0, 0, window.innerWidth, window.innerHeight / 2);
                preSnapped = snapped;
            } else if (b.left < MARGINS) {
                // hintLeft();
                setBounds(pane, 0, 0, window.innerWidth / 2, window.innerHeight);
                preSnapped = snapped;
            } else if (b.right > rightScreenEdge) {
                // hintRight();
                setBounds(pane, window.innerWidth / 2, 0, window.innerWidth / 2, window.innerHeight);
                preSnapped = snapped;
            } else if (b.bottom > bottomScreenEdge) {
                // hintBottom();
                setBounds(pane, 0, window.innerHeight / 2, window.innerWidth, window.innerWidth / 2);
                preSnapped = snapped;
            } else {
                preSnapped = null;
            }

            hintHide();

        }

        clicked = null;

    }
</script>
</body>
</html>