JSFiddle - React, Tailwind, and code Playground

HTML

<select name="sex">
    <option value="male">Male</option>
    <option value="female">Female</option>
</select>
<input type="text" name="pronoun" value="" placeholder="pronoun" />

JavaScript

$("select[name=sex]").change(function () {
    $('input[name=pronoun]').val((this.value == 'male') ? "His" : "Her")
});