Why does my page fall into the infinite loop?

function randomNumber(){
    var value;
    var flag = false;
    var tds = document.querySelectorAll('td');
    do{
        value = Math.round(Math.random() * (26 - 1) + 1);
        for(var t = 0; t < tds.length; t++){
            if(tds[t].innerHTML == value)
                flag = true;
        }
        if(!flag){
            return value;
        }
    }while(flag == true)
}

This function returns a random number for innerHTML of a new td. In case there are other tds with the same number as this code generates, the loop starts once again. If the generated number is unique, I add it to the innerHTML of a new td. But I can't even load the page since I run into an infinite loop, but no matter how hard I tried, I couldn't notice the problem in logic of this code.