LeetCode/reverse-integer/nodejs/index.js

/*
Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

Input: 123
Output: 321
Example 2:

Input: -123
Output: -321
Example 3:

Input: 120
Output: 21
Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
*/

const { assert }  = require('../../util/js'); 

/**
 * @param {number} x
 * @return {number}
 */
const reverse = function(x) {
  const MAX_INT = Math.pow(2,31) -1;
  const MIN_INT = Math.pow(2,31)* -1;

  const X = x.toString();
  
  const isNeg = X[0] === '-';
  let reverseIntegerString = X.split('').reverse().join('');

  const reverseInteger = isNeg ? parseInt(reverseIntegerString) * -1 : parseInt(reverseIntegerString);

  return (reverseInteger >= MAX_INT || reverseInteger <= MIN_INT) ?  0 :  reverseInteger;
};

/* Test Case 1
 * Input:  123
 * Output: 321
 */
x = 123;
sol = 321;
assert(reverse(x) === sol, 'Output: 321');

/* Test Case 2
 * Input: -123
 * Output: -321
 */
x = -123;
sol = -321
assert(reverse(x) === sol, 'Output: -321');

/* Test Case 3
 * Input: 120
 * Output: 21
 */
x = 120;
sol = 21;
assert(reverse(x) == sol, 'Output: 21');