examples/mouse-draw-polyline.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>SVG使用鼠标点击绘制折线效果</title>
</head>
<body>
<div id="box">
    <svg id="svg" xmlns="http://www.w3.org/2000/svg" width="600" height="600" style="border: 1px solid #000"></svg>
</div>
<script>
window.onload = () => {
    var ming = 'http://www.w3.org/2000/svg'
    var oSvg = document.getElementById('svg')
    var oPolyLine = null
    var pointsNum = ''
    var box = document.getElementById('box')

    box.appendChild(createTag('svg', {'xmlns': ming}))
    oSvg.onmousedown = event => {
        var x = event.clientX - box.offsetLeft
        var y = event.clientY - box.offsetTop

        if(!oPolyLine){
            oPolyLine = createTag('polyline', {
                'fill': 'none',
                'stroke': 'red',
                'stroke-width': 2
            })
            oSvg.appendChild(oPolyLine)
        }

        if(pointsNum == ''){
            pointsNum = `${x},${y}`
        }else{
            pointsNum += `,${x},${y}`
        }

        oPolyLine.setAttribute('points', pointsNum)
        var oCircle = createTag('circle', {
            'cx': x,
            'cy': y,
            'r': 5,
            'fill': 'white',
            'stroke': 'red',
            'stroke-width': 3
        })
        oSvg.appendChild(oCircle)

        if(event.button == 2){
            oSvg.onmousemove = null
            oSvg.oncontextmenu = () => {
                oSvg.onmousemove = null
                return false
            }
        }else{
            oSvg.onmousemove = event => {
                if(oPolyLine){
                    let x = event.clientX - box.offsetLeft
                    let y = event.clientY - box.offsetTop
                    oPolyLine.setAttribute('points', `${pointsNum},${x},${y}`)
                }
            }
        }
    }

    function createTag(tagName, tagAttr){
        var tag = document.createElementNS(ming, tagName)
        for(let attr in tagAttr){
            tag.setAttribute(attr, tagAttr[attr])
        }
        return tag
    }
}
</script>

</body>
</html>