fetch api returns `function text() { [native code] }` : <p>im new with fetch api and i've got a tiny problem.</p>

<pre><code>document.getElementById('getText').addEventListener('click',function(){
    fetch('text.txt')
        .then(function(res){
            return res.text
        }).then(function(data){
            document.body.innerHTML += `&lt;br&gt;&lt;br&gt;${data}`
        })
        .catch(function(err){
            console.log(err)
        })
})

</code></pre>

<p>this is my code. it returns this: 
<code>function text() { [native code] }</code>
i want it to returns the content not this. i dont know what should i do !?
sorry for asking a dumb question.
thanks</p>
