getelementsbytagname in JavaScript

Question

Below is the code I’ve in JavaScript: 

 var btn = document.getElementsByTagName('button');

console.log(btn);

 

btn.onclick=function(){

    alert('entered');

document.getElementById("demo").innerHTML="test";

}

But “getElementsByTagName” is not working. Can anyone tell me what I’m doing wrong here? 

Answer 1

Use the below code:

var btn = document.getElementsByTagName('button')[0];

This returns an array of matched elements. The ‘0’ index to access the button. 

You can also specify ID on button by this getElementById() like below:

JS: 

var btn = document.getElementById('myButton');

HTML: 

<button id="myButton">....</button>

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