Question

嘿，我想使用lodash从对象数组中计算一个属性的总和

假设对象数组看起来像这样...

#find all your connected components (white blobs in your image)
nb_components, dotput, stats, centroids = cv2.connectedComponentsWithStats(thresh, connectivity=8)
#connectedComponentswithStats yields every seperated component with information on each of them, such as size
#the following part is just taking out the background which is also considered a component, but most of the time we don't want that.
sizes = stats[1:, -1]; nb_components = nb_components - 1

# minimum size of particles we want to keep (number of pixels)
#here, it's a fixed value, but you can set it as you want, eg the mean of the sizes or whatever
min_size = 50

#your answer image
img2 = numpy.zeros((dotput.shape))
#for every component in the image, you keep it only if it's above min_size
#thresh[output == 5 + 1] = 0
dots = []
for i in range(0, nb_components):
    if sizes[i] < min_size:
        dots.append(centroids[i])

#print(dots)
if dots:
    dots.sort(key = lambda x: abs(x[1]-digitCenY))
    print(dots)
    pDot = -1

    for i in range(len(digitCenX)):
        if (dots[0][0] <= digitCenX[i]) and (i > 0):
            pDot = 0
            break
        elif (digitCenX[i] <= dots[0][0]) and (i != len(digitCenX)-1):
            pDot = 0
            break
        else:
            pDot = 1

    cv2.rectangle(output, (int(dots[pDot][0]), int(dots[pDot][1])), (int(dots[pDot][0]) + 3, int(dots[pDot][1]) + 3), (0, 255, 0), 1)

我想使用lodash计算该对象的'牛奶'总和。

Answer 1

类似这样的东西

const bills = salary.map((s)=> s.bills)

_(bills).map((objs,key)=>({
    'milk': _.sumBy(objs, 'milk')
})).value

Answer 2

使用嵌套的_.sumBy()调用。内部人员从一个milk中获得salary的总和，外部人员将所有薪金相加：

const data = {"salary":[{"bills":[{"electricity":300,"milk":500},{"electricity":240,"milk":200},{"electricity":800,"milk":900}]}]}

const result = _.sumBy(data.salary, ({ bills }) => _.sumBy(bills, 'milk'))

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.js"></script>

如何仅使用lodash从对象数组求和？

2 个答案: