JavaScript字符串处理：高效替换空格为加号并去除首尾空白

let str = "blah blah blah   ";
let res = str.replace(/\s+/g, '+');
console.log(res);
// 实际输出: "blah+blah+blah+"
// 预期输出: "blah+blah+blah"

let strWithTrailingSpaces = "  hello world   ";
let trimmedStr = strWithTrailingSpaces.trim();
console.log(trimmedStr); // 输出: "hello world"

let strExample = "blah blah blah   ";
let afterTrim = strExample.trim();
console.log(afterTrim); // 输出: "blah blah blah"

let strWithInternalSpaces = "blah   blah  blah";
let replacedStr = strWithInternalSpaces.replace(/\s+/g, '+');
console.log(replacedStr); // 输出: "blah+blah+blah"

let str = "blah blah blah   ";

// 先去除首尾空白，再替换内部空白
let res = str.trim().replace(/\s+/g, '+');

console.log(res);

/**
 * 格式化字符串：去除首尾空白，并将内部连续空白替换为加号。
 * @param {string} inputStr 待处理的字符串。
 * @returns {string} 格式化后的字符串。
 */
function formatSpacesToPlus(inputStr) {
  if (typeof inputStr !== 'string') {
    console.warn("输入不是字符串类型，尝试转换为字符串。");
    inputStr = String(inputStr);
  }
  return inputStr.trim().replace(/\s+/g, '+');
}

// 测试用例
let testStr1 = "blah blah blah   ";
console.log(`原始字符串: "${testStr1}"`);
console.log(`格式化后: "${formatSpacesToPlus(testStr1)}"`); // 预期: "blah+blah+blah"

let testStr2 = "  leading and trailing spaces  ";
console.log(`原始字符串: "${testStr2}"`);
console.log(`格式化后: "${formatSpacesToPlus(testStr2)}"`); // 预期: "leading+and+trailing+spaces"

let testStr3 = "no_spaces_here";
console.log(`原始字符串: "${testStr3}"`);
console.log(`格式化后: "${formatSpacesToPlus(testStr3)}"`); // 预期: "no_spaces_here"

let testStr4 = "   only   spaces   ";
console.log(`原始字符串: "${testStr4}"`);
console.log(`格式化后: "${formatSpacesToPlus(testStr4)}"`); // 预期: "only+spaces"

let testStr5 = "";
console.log(`原始字符串: "${testStr5}"`);
console.log(`格式化后: "${formatSpacesToPlus(testStr5)}"`); // 预期: ""

let testStr6 = " ";
console.log(`原始字符串: "${testStr6}"`);
console.log(`格式化后: "${formatSpacesToPlus(testStr6)}"`); // 预期: ""

原始字符串: "blah blah blah   "
格式化后: "blah+blah+blah"
原始字符串: "  leading and trailing spaces  "
格式化后: "leading+and+trailing+spaces"
原始字符串: "no_spaces_here"
格式化后: "no_spaces_here"
原始字符串: "   only   spaces   "
格式化后: "only+spaces"
原始字符串: ""
格式化后: ""
原始字符串: " "
格式化后: ""