javascript - 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)
}));

标签： javascriptarraystofixed

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);