You can find all the code in this post at repo Github.

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String related challenges

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Is alphanumeric

/**
 * @param {any} char
 * @return {Boolean}
 */

function isAlphaNumeric(char) {
  return /[A-Za-z0-9]/.test(char);
}

// Usage example
console.log(isAlphaNumeric("a")); // => true
console.log(isAlphaNumeric(0)); // => true
console.log(isAlphaNumeric("!")); // => false

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Camel case Snake case

// camel case to snake case
/**
 * @param {string} str
 * @return {string}
 */
function toKebabCase(str) {
  let temp = str.replace(/[A-Z]/g, function (i) {
    return "_"   i.toLowerCase();
  });

  if (temp[0] === "_") {
    temp = temp.slice(1);
  }

  return temp;
}

// Usage example
console.log(toKebabCase("testMethod")); // => "test_method"

// snake case to camel case
/**
 * @param {string} str
 * @return {string}
 */
function toCamelCase(str) {
  return str.replace(
    /([a-z])_([a-z])/gi,
    (_, left, right) => left   right.toUpperCase()
  );
}

// Usage example
console.log(toCamelCase("test_method")); // => "testMethod"

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Compare version numbers

/**
 * @param {string} version1
 * @param {string} version2
 * @return {number}
 */

function compareVersion(version1, version2) {
  const v1Arr = version1.split(".");
  const v2Arr = version2.split(".");

  for (let i = 0; i  v2Num) {
      return 1;
    } else if (v1Num  1, meaning first one is greater
console.log(compareVersion("12.1.0", "12.1.2")); // => -1, meaning latter one is greater
console.log(compareVersion("5.0.1", "5.0.1")); // => 0, meaning they are equal.

---

Version numbers sorting

/**
 * @param {string[]} versions
 * @return {string[]}
 */

function sortVersions(versions) {
  return versions.sort((a, b) => {
    const aParts = a.split(".").map(Number);
    const bParts = b.split(".").map(Number);

    for (let i = 0; i  [ '0.1.1', '0.302.1', '2.3.3', '4.2', '4.3.4.5', '4.3.5' ]

---

Compress a string

/**
 * @param {string} str
 * @return {string}
 */

function compress(str) {
  if (!str) {
    return "";
  }

  let compressed = "";
  let count = 1;

  for (let i = 1; i  1) {
        compressed  = count;
      }
      count = 1;
    }
  }

  return compressed;
}

// Usage example
console.log(compress("a")); // 'a'
console.log(compress("aa")); // 'a2'
console.log(compress("aaa")); // 'a3'
console.log(compress("aaab")); // 'a3b'
console.log(compress("aaabb")); // 'a3b2'
console.log(compress("aaabba")); // 'a3b2a'

/** * @param {string} str * @return {string} */ function compress(str) { if (!str) { return ""; } let compressed = ""; let count = 1; for (let i = 1; i 1) { compressed = count; } count = 1; } } return compressed; } // Usage example console.log(compress("a")); // 'a' console.log(compress("aa")); // 'a2' console.log(compress("aaa")); // 'a3' console.log(compress("aaab")); // 'a3b' console.log(compress("aaabb")); // 'a3b2' console.log(compress("aaabba")); // 'a3b2a'

---

Uncompress a string

/**
 * @param {string} str
 * @return {string}
 */

function compress(str) {
  if (!str) {
    return "";
  }

  let compressed = "";
  let count = 1;

  for (let i = 1; i  1) {
        compressed  = count;
      }
      count = 1;
    }
  }

  return compressed;
}

// Usage example
console.log(compress("a")); // 'a'
console.log(compress("aa")); // 'a2'
console.log(compress("aaa")); // 'a3'
console.log(compress("aaab")); // 'a3b'
console.log(compress("aaabb")); // 'a3b2'
console.log(compress("aaabba")); // 'a3b2a'

/** * @param {string} str * @returns {string} */ function uncompress(str) { const stack = []; let currentNum = 0; let currentStr = ""; for (const char of str) { if (char >= "0" && char 'ababab' console.log(uncompress("3(ab2(c))")); // => 'abccabccabcc'

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Find the length of the longest word in a string

/**
 * @param {string} str
 * @return {string}
 */

function compress(str) {
  if (!str) {
    return "";
  }

  let compressed = "";
  let count = 1;

  for (let i = 1; i  1) {
        compressed  = count;
      }
      count = 1;
    }
  }

  return compressed;
}

// Usage example
console.log(compress("a")); // 'a'
console.log(compress("aa")); // 'a2'
console.log(compress("aaa")); // 'a3'
console.log(compress("aaab")); // 'a3b'
console.log(compress("aaabb")); // 'a3b2'
console.log(compress("aaabba")); // 'a3b2a'

/** * @param {string} str * @return {number} */ function longestLength(str) { const strArr = str.split(" "); let length = 0; for (let i = 0; i length) { length = strArr[i].length; } } return length; } // Usage example console.log(longestLength("The longest word is thelongestword")); // => 14

---

Find the word with longest length in a string

/**
 * @param {string} str
 * @return {string}
 */

function compress(str) {
  if (!str) {
    return "";
  }

  let compressed = "";
  let count = 1;

  for (let i = 1; i  1) {
        compressed  = count;
      }
      count = 1;
    }
  }

  return compressed;
}

// Usage example
console.log(compress("a")); // 'a'
console.log(compress("aa")); // 'a2'
console.log(compress("aaa")); // 'a3'
console.log(compress("aaab")); // 'a3b'
console.log(compress("aaabb")); // 'a3b2'
console.log(compress("aaabba")); // 'a3b2a'

/** * @param {string} str * @return {string[]} */ function longestWord(str) { const strArr = str.split(" "); const result = []; let max = 0; for (const char of strArr) { if (char.length > max) { max = char.length; } } for (const char of strArr) { if (char.length === max) { result.push(char); } } return result.join(""); } // Usage example console.log(longestWord("The longest word is thelongestword")); // => "thelongestword"

---

Most frequently occurring character

/**
 * @param {string} str
 * @return {string}
 */

function compress(str) {
  if (!str) {
    return "";
  }

  let compressed = "";
  let count = 1;

  for (let i = 1; i  1) {
        compressed  = count;
      }
      count = 1;
    }
  }

  return compressed;
}

// Usage example
console.log(compress("a")); // 'a'
console.log(compress("aa")); // 'a2'
console.log(compress("aaa")); // 'a3'
console.log(compress("aaab")); // 'a3b'
console.log(compress("aaabb")); // 'a3b2'
console.log(compress("aaabba")); // 'a3b2a'

/** * @param {string} str * @returns {string | string[]} */ function count(str) { const map = new Map(); const result = []; for (const char of str) { map.set(char, (map.get(char) ?? 0) 1); } const max = Math.max(...map.values()); for (const [key, value] of map) { if (value === max) { result.push(key); } } return result.length === 1 ? result[0] : result; } // Usage example console.log(count("abbccc")); // => 'c' console.log(count("abbcccddd")); // => ['c', 'd'];

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Get string length(support emojis)

/**
 * @param {string} str
 * @return {string}
 */

function compress(str) {
  if (!str) {
    return "";
  }

  let compressed = "";
  let count = 1;

  for (let i = 1; i  1) {
        compressed  = count;
      }
      count = 1;
    }
  }

  return compressed;
}

// Usage example
console.log(compress("a")); // 'a'
console.log(compress("aa")); // 'a2'
console.log(compress("aaa")); // 'a3'
console.log(compress("aaab")); // 'a3b'
console.log(compress("aaabb")); // 'a3b2'
console.log(compress("aaabba")); // 'a3b2a'

/** * @param {String} str * @return {Number} */ function getStringLength(str) { return Array.from(new Intl.Segmenter().segment(str)).length; } // Usage example console.log(getStringLength("test?")); // => 5 console.log("test?".length); // => 6

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Reference

Alphanumericals - Wikipedia.org
Naming convention (programming) - Wikipedia.org
79. convert snake_case to camelCase - BFE.dev
Software versioning - Wikipedia.org
157. semver compare - BFE.dev
165. Compare Version Numbers - LeetCode
97. compress a string - BFE.dev
173. uncompress string - BFE.dev
145. most frequently occurring character -BFE.dev