My input-function in javascript always return false, even when a user inputs the correct value

Thanks for being able to help!

I want to know why my function always returns false, and how I can fix it. At first i thought it had something to do with my syntax at check = ("stairway to heaven"===value || "Stairway to heaven"===value);. But no matter how i put it, it's always false.

I tried reading into This, but as far as I could understand, it doesn't help me.

I've created this in javascript to do different things depending on if the result of check is true or false.

else if (textNodes[15].id === 16 && nextTextNodeId === 16)  {
        showSongContainer();
        if(check) {
            showTextNode(17);
        }
        if (!check) {
            textElement.innerText = 'That’s superwrong! Maybe if you would use that small brain of yours you’d figure it out!';
            showTextNode(11);
        }

The above code runs this function first, to determine if a text input returns true (stairway to heaven) or false (anything other than stairway to heaven):

function showSongContainer() {
    songContainer.style.display = 'unset';
    const songInput = document.getElementById('songInput');
    const songButton = document.getElementById('songButton');

    songButton.addEventListener('click', (e) => {
        e.preventDefault();
        let value = songInput.value;
       
     check = ("stairway to heaven"===value || "Stairway to heaven"===value);
    });
} 

However, when the first else if starts (in the first codeblock), it always goes to the if (!check), before the text input has even been entered. Why is this? And how do I make it so that it returns the first if (in the first code block) if the text input is correct, and the other if, if incorrect?

I also have let check = ''; in a global scope in the begining of my code, if that has anything to do with it.

Im pretty new to coding, so please dont be too harsh :D

Let me know if you need any additional information.

Cheers.