Successding calls to value() return different results

[ceving]

I have the following example:

#! /usr/bin/node

const OptionParser = require ('option-parser');
const options = new OptionParser ();

const search_option = options
      .addOption ('s', 'search', 'Search')
      .argument ('JQL');

options.parse ();

var s1 = search_option.value();
var s2 = search_option.value();

console.log (s1 == s2);

When I run it, it displays false.

$ ./example -s xxx
false

How is this possible?

$ npm list
/home/szi
├─┬ jsdoc3-bootstrap@0.15.0
│ ├── bootstrap@3.4.1
│ └── dotenv@0.4.0
└── option-parser@1.0.2
$ npm --version
6.14.8
$ node --version
v10.24.0
$ uname -a
Linux kallisto 4.19.0-18-amd64 #1 SMP Debian 4.19.208-1 (2021-09-29) x86_64 GNU/Linux