How can I select all elements with the same class name?

Question

I have a Boolean variable. It is stored in a hidden input field. Basically, if the user is signed in, it is false, if not, it is true.

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Answer 1

if (document.getElementById('download_btn_var_input').value == "true") {
    var el = document.getElementsByClassName('project_download_btn');
    for (var i = 0; i < el.length; i++) {
        el[i].hidden = true;
    }
}

Answer 2

document.getElementsByClassName returns array so what you are interested is :

document.getElementsByClassName('project_download_btn')[0]

Answer 3

Loop through each div that contains your download button and set hidden to true:

if (document.getElementById('download_btn_var_input').value == "true") {
    var button_divs_array = document.getElementsByClassName('project_download_btn');
    for (var i = 0; i < button_divs_array.length; i++) {
        button_divs_array[i].hidden = true;
    }
}

Answer 4

You can simply loop through the elements instead of just taking the 0th.

var buttons = document.getElementsByClassName('project_download_btn');

for(var i=0; i< buttons.length; i++){
    buttons[i].hidden = true;
}