无痕埋点之XPath

在这里我们是用XPath来标识页面元素、控件的唯一性

XPath

至于什么是XPath，可以自行google。chrome有它算出XPath的功能！打开一个网页，F12，在弹出的小窗口中选中一个标签，右键，看到“copy XPath”了吧！点下然后粘贴下就知道这元素的标签的XPath多少了

Javascript get XPath and find element by XPath

Chrome浏览器中通过js获取xpath和根据xpath获取元素

export default {
    getXPath(elm){
        let allNodes = document.getElementsByTagName('*')
        for(var segs = []; elm && elm.nodeType == 1; elm = elm.parentNode){
            if(elm.hasAttribute('id')){
                let uniqueIdCount = 0
                for(var n=0;n < allNodes.length;n++){
                    if (allNodes[n].hasAttribute('id') && allNodes[n].id == elm.id) uniqueIdCount++;
                    if (uniqueIdCount > 1) break;
                }
                if(uniqueIdCount == 1){
                    segs.unshift('//*[@id="' + elm.getAttribute('id') + '"]');
                    return segs.join('/');
                }else{
                    return false
                }
            }else{
                for(var i = 1, sib = elm.previousSibling; sib; sib = sib.previousSibling){
                    if (sib.localName == elm.localName)  i++;
                }
                if(i == 1){
                    if(elm.nextElementSibling){
                        if(elm.nextElementSibling.localName != elm.localName){
                            segs.unshift(elm.localName.toLowerCase())
                        }else{
                            segs.unshift(elm.localName.toLowerCase() + '[' + i + ']');
                        }
                    }else{
                        segs.unshift(elm.localName.toLowerCase())
                    }
                }else{
                    segs.unshift(elm.localName.toLowerCase() + '[' + i + ']');
                }
            }
        }
        return segs.length ? '/' + segs.join('/') : null
    },
    getElem(path){
        try{
            var evaluator = new XPathEvaluator();
            var result = evaluator.evaluate(path, document.documentElement, null,XPathResult.FIRST_ORDERED_NODE_TYPE, null);
            return  result.singleNodeValue || '';
        }catch(e){
            return ''
        }
    }
}