map.data.addListener('click', function(event) {
var altitudeMode = event.feature.getProperty('altitudeMode') === undefined || null ?
""
:
"<tbody>"+"<th>altitudeMode:</th>" + "<td>" + event.feature.getProperty('altitudeMode') + "</td>" + "</tbody>";
}
[当我尝试检查值是否为未定义或为null时,将检查未定义的变量,而不是null值,我正在Google地图的点击处理程序中执行此操作map.data.addListener('click',...
(property === undefined) || (null)
,不测试该属性是否未定义或为空。为此,只需编写null
值添加单独的严格比较: