en boucle sur le bouton donne toujours 0 réponse

Question

Voici le code. Merci de m'aider.

/*this code works fine in code snippet and (when I run the code in the chrome console but when I write the code in my file.js, this won't work*/ 
 
var btn = document.getElementsByTagName('button'); 
 
alert(btn.length); 
 
// it must alert 3, but I always get 0. Please help me. Thank you

<button>Games</button> 
 
<button>Foods</button> 
 
<button>Movies</button>

Answer 1

Exécutez les js après le document prêt .use avec window.onload fonction

window.onload=function(){ 
 
var btn = document.getElementsByTagName('button'); 
 
alert(btn.length); 
 
}

<button>Games</button> 
 
<button>Foods</button> 
 
<button>Movies</button>