Reverse Integer
<p>Given a signed 32-bit integer <code>x</code>, return <code>x</code><em> with its digits reversed</em>. If reversing <code>x</code> causes the value to go outside the signed 32-bit integer range <code>[-2<sup>31</sup>, 2<sup>31</sup> - 1]</code>, then return <code>0</code>.</p>

<p><strong>Assume the environment does not allow you to store 64-bit integers (signed or unsigned).</strong></p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> x = 123
<strong>Output:</strong> 321
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> x = -123
<strong>Output:</strong> -321
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> x = 120
<strong>Output:</strong> 21
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>-2<sup>31</sup> &lt;= x &lt;= 2<sup>31</sup> - 1</code></li>
</ul>
Math
/**
 * @param {number} x
 * @return {number}
 */
var reverse = function (x) {
    const mi = -(2 ** 31);
    const mx = 2 ** 31 - 1;
    let ans = 0;
    for (; x != 0; x = ~~(x / 10)) {
        if (ans < ~~(mi / 10) || ans > ~~(mx / 10)) {
            return 0;
        }
        ans = ans * 10 + (x % 10);
    }
    return ans;
};
