JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" style="width:20%;" class="input-text" name="position[]" value="20" />
 <input type="text" style="width:20%;" class="input-text" name="position[]" value="25" />
 <input type="text" style="width:20%;" class="input-text" name="position[]" value="10" />
 <input type="text" style="width:20%;" class="input-text" name="position[]" value="5" />
 <input type="text" style="width:20%;" class="input-text" name="position[]" value="30" />

JavaScript

$(function() {
    Array.max = function( array ){
        return Math.max.apply(Math, array );
    };
    
    var max = Array.max($('.input-text').map(function() {
        return $(this).val();
    }));
    
    console.log(max)
})