javascript - javascript 或 nodejs 是否有索引范围来访问数组项？

Question

我在ruby中看到了这段代码

module Plutus
  TAX_RATES = {
    (0..18_200)                => { base_tax_amount:      0, tax_rate: 0 },
    (18_201..37_000)           => { base_tax_amount:      0, tax_rate: 0.19 },
    (37_001..80_000)           => { base_tax_amount:  3_572, tax_rate: 0.325 },
    (80_001..180_000)          => { base_tax_amount: 17_547, tax_rate: 0.37 },
    (180_001..Float::INFINITY) => { base_tax_amount: 54_547, tax_rate: 0.45 }
  }.freeze
end

当值落在范围内时，它似乎能够访问数组项。

例如给定 18000，可以得到 {base_tax_amount: 0, tax_rate: 0}。

在 javascript 或 nodejs 中是否有任何等效项？

Answer 1

没有，没有那个界面。
您必须重新计算索引或使用 Proxy :

const TaxRates = new Proxy({}, {
  get(target, prop) {
    switch (true) {
      case prop < 18200:  return { base_tax_amount: 0,     tax_rate: 0 };
      case prop < 37000:  return { base_tax_amount: 0,     tax_rate: 0.19 };
      case prop < 80000:  return { base_tax_amount: 3572,  tax_rate: 0.325 };
      case prop < 180000: return { base_tax_amount: 17547, tax_rate: 0.37 };
      default:            return { base_tax_amount: 54547, tax_rate: 0.45 };
    }    
  }
});

console.log([
  TaxRates[18000],
  TaxRates[35000],
  TaxRates[55000],
  TaxRates[550000],
]);