使用reduce方法JS后的toFixed

Question

我正在映射一个数组并将 50 个项目减少到 1 - 它们的总和。那 50 个项目是浮点精度数。请帮忙，我不明白我应该在该地图的哪个位置放置固定（2），以获得正确的 summaryIncome 属性，而不是像这样：39990,89999999999913。var data = [  {id: 1, incomes: [{value:1}, {value: 2}]},   {id: 2, incomes: [{value:2}, {value: 3}]}],  ...]var summary = data.map(item => ({  ...item,  summaryIncome: item.incomes.reduce((acc, income) =>    acc += income.value, 0)}));

Answer 1

为了保持总和准确，请toFixed在总结所有values 后调用：

var data = [

  {id: 1, incomes: [{value: 0.1}, {value: 0.2}]}, 

  {id: 2, incomes: [{value:2}, {value: 3}]},

]

var summary = data.map(item => ({

  ...item,

  summaryIncome: item.incomes.reduce((acc, income) => acc + income.value, 0).toFixed(2)

}));

console.log(summary);

仅在必要时输入小数点：

var data = [

  {id: 1, incomes: [{value: 0.1}, {value: 0.2}]}, 

  {id: 2, incomes: [{value:2}, {value: 3}]},

]

var summary = data.map(item => ({

  ...item,

  summaryIncome: (() => {

    const trueSum = item.incomes.reduce((acc, income) => acc + income.value, 0);

    return Number.isInteger(trueSum) ? String(trueSum) : trueSum.toFixed(2);

  })()

}));

console.log(summary);