javascript - 无法使用其密钥访问对象的属性？

Question

在谷歌地球编辑器中，我们创建使用reduceRegion（）函数的对象：

var meanValue2015 = ndvi2015.reduceRegion({ 
    reducer: ee.Reducer.mean(), 
    geometry: justEC15.geometry(), 
    crs: 'EPSG:4326', 
    scale: 30, 
}); 

我的问题是，meanValue2015似乎是一个对象 - 我输入

print(meanValue2015); 
print(typeof(meanValue2015)); 
print(Object.keys(meanValue2015)); 

，并获得“ Object（1 property） - NDVI：0.3177 ...“，”Object“，然后是”[]“？然后

print(meanValue2015.NDVI); 
print(meanValue2015['NDVI']); 

是未定义？有什么明显的我在这里做错了吗？

Answer 1

meanValue2015是一个地球引擎对象：一个字典。所以..

var meanValue2015 = ndvi2015.reduceRegion({ 
    reducer: ee.Reducer.mean(), 
    geometry: justEC15.geometry(), 
    crs: 'EPSG:4326', 
    scale: 30, 
}); 

var realValue = ee.Number(meanValue2015.get("ndvi")); 
print("real value (object):", realValue) 

// realValue is a EE object, so you have to use it as is.. 
// this would be easy, but it is wrong.. 
var newValueWrong = realValue + 1 

// this is the right way.. 
var newValueRight = realValue.add(ee.Number(1)) 

print("wrong:", newValueWrong) 
print("right:", newValueRight) 

// there is another way, but it is not recommendable because you'd 
// be wasting EE computing capacity (Google's gift! don't waste it) 

var localValue = realValue.getInfo() + 1 

print("value in the local scope (try to avoid)", localValue)