String prototype - JavaScript Challenges

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

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String prototype related challenges

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String.prototype.repeat()

The key here is to handle different edge cases.

/**
 * @param {number} count
 * @return {string}
 */

// Time: O(1) | Space: O(1)
String.prototype.myRepeat = function (count) {
  if (count < 0) {
    throw new RangeError("count must be non-negative");
  }

  if (count === 0) {
    return "";
  }

  return Array.from({ length: Math.round(count) + 1 }).join(this);
};

// Usage example
console.log("abc".myRepeat(0)); // => ""
console.log("abc".myRepeat(1)); // => "abc"
console.log("abc".myRepeat(2)); // => "abcabc"
console.log("abc".myRepeat(-1)); // => RangeError

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String.prototype.trim()

Use regular expressions to make your day easier:

• // for regular expression
• ^ matches the beginning
• $ matches the ending
• g matches all the patterns
• | acts like logic OR operator
• + means one or more characters
• \s matches all whitespace(spaces, tabs, line breaks)

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

// Time: O(1) | Space: O(1)
String.prototype.myTrim = function () {
  return this.replace(/^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g, "");
  // or
  // return this.replace(/^[\s]+|[\s]+$/g, "");
};

// Usage example
const str = "  Hello, World!  ";
console.log(str.myTrim()); // => "Hello, World!"

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Reference

• String.prototype.repeat() - MDN
• String.prototype.trim() - MDN
• 95. implement String.prototype.trim() - BFE.dev