用于确定数值属于哪个范围的优雅解决方案

Question

如果我为函数提供一个数字，我将如何根据这样的数字范围来验证它？

1-10  = A
11-20 = B
21-30 = C
...

我知道我可以做if语句来评估这一点，但我正在寻找更优雅的东西，因为问题变得更加复杂，我不想要一个讨厌的 if 网络。

var letter = "";
function getLetter(num) {
if (num >= 1 && num <= 10) {
letter = "A";
} else if (num >= 11 && num <= 20) {
letter = "B";
}
// this eventually gets gross
}

getLetter(14)的预期结果将是"B"，getLetter(49)将是"E"，等等。

欢迎任何其他想法。

Answer 1

只是关于你的代码的一点

function getLetter(num) {
if (num >= 1 && num <= 10) {
letter = "A";
} else if (num >= 11 && num <= 20) {
letter = "B";
}
// this eventually gets gross
}

这可以简化为

function getLetter(num) {
if (num >= 1) {
if(num <= 10) {
letter = "A";
} else if (num <= 20) {
letter = "B";
}
// this eventually gets gross too
}
}

但：

如果它像每个字母代表 10 个值的范围一样简单：

function getLetter(num) {
return String.fromCharCode(65 + Math.floor((num - 1) / 10));
}
console.log(getLetter(1));
console.log(getLetter(14));
console.log(getLetter(49));

或按照建议

function getLetter(num) {
const ret = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
return ret[Math.floor((num - 1) / 10)] || "+"; // greater than 260
}
console.log(getLetter(1));
console.log(getLetter(14));
console.log(getLetter(49));
console.log(getLetter(261));

function getLetter(number) {
let ranges = {
a: 10,
b: 20,
c: 30,
underflow: 0,
overflow: Infinity
}
return Object.entries(ranges)
.sort(([ka, va], [kb, vb]) => va - vb) // because object key sort order isn't guaranteed
// though it will be in the order as declared, but
// sorting makes sense
.find(([key, value]) => number <= value)[0];
}
console.log(getLetter(5))
console.log(getLetter(17))
console.log(getLetter(20))
console.log(getLetter(30))
console.log(getLetter(31))
console.log(getLetter(0))

如果范围是连续的，则只需要其中一个边界

Answer 2

如果你想把你的范围放到一个对象中，然后循环访问它，工作正常

function getLetter (number) {
let ranges = {
a: [1, 10],
b: [11, 20],
c: [21, 30],
d: [31, 36],
e: [37, 40]
}
return Object.keys(ranges).find((key) => {
let currRange = ranges[key];
if (number >= currRange[0] && number <= currRange[1]) {
return key;
}
});
}
console.log(getLetter(5))
console.log(getLetter(17))
console.log(getLetter(20))
console.log(getLetter(30))
console.log(getLetter(35))
console.log(getLetter(39))