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console 命令行工具 X clear

                    
>
console
{
    document.addEventListener('mousedown', e=>{
        let strPos = {
            x: e.pageX,
            y: e.pageY
        };
        let oDiv = document.createElement('div');
        document.body.appendChild(oDiv);

        let move = e=>{
            let nowPos = {
                x:e.clientX,
                y:e.clientY
            };
            let size = {
                w: Math.abs(nowPos.x - strPos.x),
                h: Math.abs(nowPos.y - strPos.y) 
            };
            oDiv.className = 'draw-div';
            oDiv.style.top = Math.min(strPos.y, nowPos.y) + 'px';
            oDiv.style.left = Math.min(strPos.x, nowPos.x) + 'px';
            oDiv.style.width = size.w + 'px';
            oDiv.style.height = size.h + 'px';  
        };

        document.addEventListener('mousemove', move);

        document.addEventListener('mouseup', function(){
            document.removeEventListener('mousemove', move);
        }, {once: true});
    });
    
}
<!doctype html>
<html>
    <head>
        <meta charset="utf-8">
    </head>
    <body>
	
</body>
</html>
.draw-div {
    position: absolute;
    border: 1px solid #000;
}