我的代码应该检测一个字符串是否有货币符号，但它不会检测到 £

Question

我的代码应该检测货币符号，并根据结果执行代码，但代码在任何情况下都不会检测到“£”。以下是相关代码：

let requirements = [ "£", "$" ];
let mcontent = "$£50";
let y = 0;
for (let p = 0; p < requirements.length; ++p) {
    if (mcontent.includes(requirements[p])) {
        ++y;
    }
}
if (y == 1) {
    //this is considered success, only ONE currency symbol was detected. If mcontent = '$50' or '£50', we should be here.
} else {
    //this is considered failure, TWO or ZERO currency symbols were detected. In this scenario, I want the code to fail.
}

我知道这可能不是编写函数以完成我想要完成的任务的最佳方式，因此我愿意为我已有的内容提供更好的想法/修复。

Answer 1

执行此操作的最简洁方法是使用RegExp 进行检查，如下所示：

if (mcontent.match(/£|\$/g)?.length == 1) { // the question mark is so we don't encounter an error if no matches were found
  // success
} else {
  // failure
}

这是一个活生生的例子：

const mcontent1 = '$£50';
const mcontent2 = '£50';
const mcontent3 = '$50';

const regex = /£|\$/g; // slash to escape $ because it has special meaning in regex

console.log(mcontent1.match(regex).length == 1); // false
console.log(mcontent2.match(regex).length == 1); // true
console.log(mcontent3.match(regex).length == 1); // true

Answer 2

如果您不想使用正则表达式，只需检查字符串是否包含符号，增加一个计数器，并返回是否正好有 1 个匹配项：

let testA = "$£50",
    testB = "£50",
    testC = "$50";

function checkString(str) {
  const symbols = ["£", "$"];
  let matches = 0;

  for (const symbol of symbols)
    if (str.includes(symbol)) matches++;
      
  return matches == 1;
}

console.log(
  checkString(testA),
  checkString(testB),
  checkString(testC)
);

Answer 3

使用 RegExp 它将根据输入的值返回 true 或 flase 这个例子会让你知道如何使用它

const elementTwo = document.getElementById('elementTwo');
elementTwo.addEventListener("input", function(event) {
  pattern = /^[£|$]{1}(\d+)/
  if (pattern.test(this.value)) {
    console.log("found")
  } else console.log("not found")

});

<p>Enter value</p>
<input id="elementTwo" type="text" />