answer of 10 leetcode challenge

TenLeetCode.js

/**
 * 58. Length of last word
 * https://leetcode.com/problems/length-of-last-word/
 */

const lengthOfLastWord = s => {
  s = s.trim().split(' ');
  const word = s[s.length - 1];
  return word.length;
};

/**
 * 66. Plus One
 * https://leetcode.com/problems/plus-one/
 */

var plusOne = function(digits) {
    const res = []
    let carriedOver = 0
    for (let x = digits.length - 1; x > -1; x--) {
      const firstNumber = x === digits.length - 1;
      
      if (carriedOver) {
        if (digits[x] + 1 > 9) {
          carriedOver = 1
          res.unshift(0);
        } else {
          res.unshift(digits[x] + 1)
          carriedOver = 0
        }
      } else {
        if (firstNumber) {
          if (digits[x] + 1 > 9) {
            carriedOver = 1
            res.unshift(0);
          } else {
            res.unshift(digits[x] + 1)
          }
        } else {
          res.unshift(digits[x])
        }
      }
    }

    if (carriedOver) {
      if (res[0] === 0) {
        res.unshift(1)
      } else {
        res[0] += 1
      }
    }
  
    return res
};

/**
 * 20. Valid Parentheses
 * https://leetcode.com/problems/valid-parentheses
 */
var isValid = function(s) {
    let stack = [], mapping = new Map([["}","{"],["]","["],[")","("]])
    for (let x = 0; x < s.length; x++) {
      if (s[x]=="(" || s[x]=="[" || s[x]=="{") stack.push(s[x])
      else {
        if (stack.pop() != mapping.get(s[x])) return false
      }
    }
    return !stack.length
};

/**
 * 35. Search Insert Position
 * https://leetcode.com/problems/search-insert-position/
 */
var searchInsert = function(nums, target) {
    const idx = nums.indexOf(target);
    if (idx > -1) {return idx}
    else if (target < nums[0]) {return 0}
    else if (target > nums[nums.length - 1]) {return nums.length}
    else {
        for (let x = 0; x < nums.length; x++) {
            if (target > nums[x] && target < nums[x+1]) {
                return x + 1
            }
        }
    }
};


/**
 * 136. Single Number
 * https://leetcode.com/problems/single-number/
 */
var singleNumber = function(nums) {
    const hash = {};
    nums.forEach(x => {
        hash[x] ? hash[x] += 1 : hash[x] = 1;
    })
    
    let y = Object.entries(hash).filter(x => x[1] === 1)[0][0];
    return y
};

/**
 * 905. Sort Array By Parity
 * https://leetcode.com/problems/sort-array-by-parity/
 */
var sortArrayByParity = function(A) {
    const even = [], odd = [];
    A.forEach(x => x % 2 === 0 ? even.push(x) : odd.push(x));
    return [...even, ...odd]
};