Question

 let data = [
 {size: 1180160, category: "Keswick", index: 1},
 {size: 1059328, category: "HCOPA", index: 2},
 {size: 30720, category: "HCOPA", index: 3},
 {size: 493056, category: "Darhan Saluja", index: 4},
 {size: 267776, category: "CRSA", index: 5},:
 {size: 328704, category: "Arundel", index: 6}
 {size: 73216, category: "Arundel", index: 7}

 data.forEach((product, index) => {
       let count = 0;
       if (product.category !== lastCategory) {            
         rows.push(
            <ProductCategoryRow 
                                category={product.category}
                                key={product.category}/>
        );
    }
    rows.push(
        <ProductRow
            product={product}
            key={product.name} count={count}/>
    );
    lastCategory = product.category;

});

我想要计算具有相同类别的计数（数量）。如果它们属于同一类别，则数量将增加。因此，它将作为道具传递给组件

Answer 1

您可以使用Array.prototype.reduce：

执行此操作

const counts = data.reduce((counts, product) => {
  counts[product.category] = (counts[product.category] || 0) + 1
  return counts
}, {})
// counts = {Arundel: 2, ...}

比创建你的元素：

let rows = []
data.forEach(product => {
  rows.push(<ProductCategoryRow category={product.category} key={product.category}>)
  rows.push(<ProductRow product={product} key={product.name} count={counts[product.categort]} />
})

Answer 2

试试这个：

 let dataArray = [
 {size: 1180160, category: "Keswick", index: 1},
 {size: 1059328, category: "HCOPA", index: 2},
 {size: 30720, category: "HCOPA", index: 3},
 {size: 493056, category: "Darhan Saluja", index: 4},
 {size: 267776, category: "CRSA", index: 5},
 {size: 328704, category: "Arundel", index: 6},
 {size: 73216, category: "Arundel", index: 7}
 ]

var d = dataArray.reduce(function (Objects, data, index) { 
  console.log(Objects)
  if (data.category in Objects) {
    Objects[data.category]++;
  }
  else {
    Objects[data.category] = 1;
  }
  dataArray[index].counts = Objects[data.category];
  return Objects;
}, {});

console.log(dataArray)

working js fiddle

如果每个项目具有相同的类别，如何计数？

2 个答案: