Change color of button with javascript

Question

I'm having trouble changing the color of a button with a simple function, the color doesn't change at all.

<html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

     <script language="JavaScript">

        function changeColor(){
             document.getElementsByTagName('button').style.backgroundColor="green";
        }

     </script>

    </head>

    <body >

        <form action="/action_page.php" method="get" name="form1">
            <input type="text" id="campoDeFlores">
            <button type="button" onclick="changeColor()" name="1">1</button>
            <button type="button"  name="2">2</button>
            <button type="button"  name="3">3</button>
        </form>
    </body>
</html>

Why does it not work?

getElementsByTagName returns an array which means you have to loop to access each element. — dokgu
– dokgu, Commented Mar 24, 2017 at 17:26

Hum4n01d · Accepted Answer · 2017-03-24 17:31:32Z

6

document.getElementsByTagName returns an list of elements not a single element. You need to convert it to an array with Array.from and then iterate over the buttons with Array.map

function changeColor(){
    Array.from(document.querySelectorAll('button')).map(function(button) {
               button.style.backgroundColor="green";
    })
}

answered Mar 24, 2017 at 17:31

Hum4n01d

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4 Comments

Nelson Teixeira Over a year ago

Just to complement: you can also do this changing document.querySelectorAll('button') to document.getElementsByTagName('button'). Also you could use .forEach instead of .map as you don't need to return a result.

Hum4n01d Over a year ago

@NelsonTeixeira I think querySelector is better because the OP might want to change the condition. Isn't forEach just ES6?

Nelson Teixeira Over a year ago

OK. Just telling the OP that option. About forEach being ES6 only, no it isn't: developer.mozilla.org/pt-BR/docs/Web/JavaScript/Reference/… (see Specifications section)

Hum4n01d Over a year ago

oh ok :D Thanks!

dokgu · Accepted Answer · 2017-03-24 17:34:31Z

Try this:

HTML

<form action="/action_page.php" method="get" name="form1">
  <input type="text" id="campoDeFlores">
  <button type="button" onclick="changeColor(this)" name="1">1</button>
  <button type="button" name="2">2</button>
  <button type="button" name="3">3</button>
</form>

JS

function changeColor(btn) {
  btn.style.backgroundColor = "green";
}

Check this Fiddle.

Explanation

At first I thought you were trying to change the color of all the buttons because you were using getElementsByTagName but it looks like you just want to change the color of the button that was pressed. In that case you don't need to use an array. Just pass the element that was clicked to the function and then change that specific button's color.

Nartub · Accepted Answer · 2017-03-24 17:35:16Z

1

You are better off using id="myButton" and document.getElementById('myButton') to specifically select a button instead of every button.

answered Mar 24, 2017 at 17:35

Nartub

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1 Comment

Adam Copley Over a year ago

This is the real solution

codneto · Accepted Answer · 2017-03-24 17:36:31Z

0

Make following changes:

allow your changeColor function to accept a HTMLElement as parameter.
Pass reference to button to changeColor(). Change onclick="changeColor()" in button element to onclick="changeColor(this)"

function changeColor (htmlEl) {
  htmlEl.style.backgroundColor="green";
}

<form action="/action_page.php" method="get" name="form1">
    <input type="text" id="campoDeFlores">
    <button type="button" onclick="changeColor(this)" name="1">1</button>
    <button type="button"  name="2">2</button>
    <button type="button"  name="3">3</button>
</form>

answered Mar 24, 2017 at 17:36

codneto

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Comments

Laxmi Kanta Dahal · Accepted Answer · 2022-05-06 03:48:59Z

0

If you have a lot of button and you want to color and uncolor it by clicking it.you can use if statement inside event listener.This feature is used specific in booking something.

HTML

<button class="btnco">1</button>
<button class="btnco">2</button>

CSS

.btnco{

     background-color: green;
    }

JS

document.querySelectorAll('.btnco').forEach(function(e) {
    e.addEventListener('click', function() {
        if (this.style.backgroundColor=="red"){
            this.style.backgroundColor="green"
        }else{
      this.style.backgroundColor = "red";
    }
    })
  });

answered May 6, 2022 at 3:48

Laxmi Kanta Dahal

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Comments

Jesús Oviedo · Accepted Answer · 2023-06-30 20:40:31Z

0

im testing *thisfunction randomcolour(){ document.getElementsByTagName('button').style.backgroundColor=${ var num = Math.floor(Math.random() * Math.pow(2, 24)); return '#' + ('00000' + num.toString(16)).substr(-6);}`;

}`*

answered Jun 30, 2023 at 20:40

Jesús Oviedo

1

1 Comment

Community Over a year ago

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