What is the best JavaScript code to create an img element

E

11

130

I want to create a simple bit of JS code that creates an image element in the background and doesn't display anything. The image element will call a tracking URL (such as Omniture) and needs to be simple and robust and work in IE 6 =< only. Here is the code I have:

var oImg = document.createElement("img");
oImg.setAttribute('src', 'http://www.testtrackinglink.com');
oImg.setAttribute('alt', 'na');
oImg.setAttribute('height', '1px');
oImg.setAttribute('width', '1px');
document.body.appendChild(oImg);

Is this the simplest but most robust (error free) way to do it?

I cannot use a framework like jQuery. It needs to be in plain JavaScript.

Everything answered 22/10, 2008 at 17:52 Comment(2)

Define "best." Fastest? Simplest? – Felker 22/10, 2008 at 18:3

@steveniseki he used en.wikipedia.org/wiki/Hungarian_notation – Trexler 1/5, 2018 at 19:11

F

103

oImg.setAttribute('width', '1px');

px is for CSS only. Use either:

oImg.width = '1';

to set a width through HTML, or:

oImg.style.width = '1px';

to set it through CSS.

Note that old versions of IE don't create a proper image with document.createElement(), and old versions of KHTML don't create a proper DOM Node with new Image(), so if you want to be fully backwards compatible use something like:

// IEWIN boolean previously sniffed through eg. conditional comments

function img_create(src, alt, title) {
    var img = IEWIN ? new Image() : document.createElement('img');
    img.src = src;
    if ( alt != null ) img.alt = alt;
    if ( title != null ) img.title = title;
    return img;
}

Also be slightly wary of document.body.appendChild if the script may execute as the page is in the middle of loading. You can end up with the image in an unexpected place, or a weird JavaScript error on IE. If you need to be able to add it at load-time (but after the <body> element has started), you could try inserting it at the start of the body using body.insertBefore(body.firstChild).

To do this invisibly but still have the image actually load in all browsers, you could insert an absolutely-positioned-off-the-page <div> as the body's first child and put any tracking/preload images you don't want to be visible in there.

Fishmonger answered 22/10, 2008 at 18:49 Comment(1)

Wouldn't just new Image() work best in all circumstances? – Flagg 31/7, 2016 at 22:20

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56

var img = new Image(1,1); // width, height values are optional params 
img.src = 'http://www.testtrackinglink.com';

Rawson answered 22/10, 2008 at 17:58 Comment(0)

O

28

var img = document.createElement('img');
img.src = 'my_image.jpg';
document.getElementById('container').appendChild(img);

Otti answered 22/10, 2008 at 18:8 Comment(1)

@AndreiCristianProdan Use console.log between each pair of lines, so you'll know exactly which line is freezing it. – Tivoli 1/8, 2019 at 12:52

A

10

jQuery:

$('#container').append('<img src="/path/to/image.jpg"
       width="16" height="16" alt="Test Image" title="Test Image" />');

I've found that this works even better because you don't have to worry about HTML escaping anything (which should be done in the above code, if the values weren't hard coded). It's also easier to read (from a JS perspective):

$('#container').append($('<img>', { 
    src : "/path/to/image.jpg", 
    width : 16, 
    height : 16, 
    alt : "Test Image", 
    title : "Test Image"
}));

Attire answered 22/10, 2008 at 18:12 Comment(2)

He specifically requested no jQuery. – Phanerozoic 29/3, 2014 at 22:30

Also, parsing text into code is pointless, ineffective and plain lazy. Whoever reads this, avoid doing it like that. I mean, if you're inserting literal <img ... /> into DOM, do it with innerHTML then. I just don't get this :/ – Liam 25/4, 2016 at 14:1

M

10

Just for the sake of completeness, I would suggest using the InnerHTML way as well - even though I would not call it the best way...

document.getElementById("image-holder").innerHTML = "<img src='image.png' alt='The Image' />";

By the way, innerHTML is not that bad

Medicaid answered 23/10, 2008 at 15:8 Comment(1)

I was using this method for a 50x50 grid of images. When I tried the above appending method my execution time jumped from 150ms to 2250ms. So I'm thinking innerHTML is much more efficient. – Farron 17/10, 2013 at 18:9

G

6

Shortest way:

(new Image()).src = "http:/track.me/image.gif";

Gershom answered 23/10, 2008 at 11:4 Comment(3)

If not added to the document, it is not certain the image src will be fetched at all (browser-dependent). – Fishmonger 23/10, 2008 at 12:26

does anyone have cases of browsers not fetching that image if not attached to the DOM? – Tovatovar 9/12, 2013 at 16:56

I've testing this in IE, FF, Chrome, and Safari—all load the image without it being appended to the DOM. Is this an issue with older browsers? – Epileptoid 30/3, 2015 at 23:39

D

4

Are you allowed to use a framework? jQuery and Prototype make this sort of thing pretty easy. Here's a sample in Prototype:

var elem = new Element('img', { 'class': 'foo', src: 'pic.jpg', alt: 'alternate text' });
$(document).insert(elem);

Deuteranope answered 22/10, 2008 at 17:53 Comment(0)

S

4

you could simply do:

var newImage = new Image();
newImage.src = "someImg.jpg";

if(document.images)
{
  document.images.yourImageElementName.src = newImage.src;
}

Simple :)

Schapira answered 15/10, 2011 at 8:16 Comment(0)

A

3

Just to add full html JS example

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>create image demo</title>
    <script>


        function createImage() {
            var x = document.createElement("IMG");
            x.setAttribute("src", "http://www.iseebug.com/wp-content/uploads/2016/09/c2.png");
            x.setAttribute("height", "200");
            x.setAttribute("width", "400");
            x.setAttribute("alt", "suppp");
            document.getElementById("res").appendChild(x);
        }

    </script>
</head>
<body>
<button onclick="createImage()">ok</button>
<div id="res"></div>

</body>
</html>

Amaurosis answered 22/10, 2016 at 12:17 Comment(0)

S

2

This is the method I follow to create a loop of img tags or a single tag as ur wish

method1 :
    let pics=document.getElementById("pics-thumbs");
            let divholder=document.createDocumentFragment();
            for(let i=1;i<73;i++)
            {
                let img=document.createElement("img");
                img.class="img-responsive";
                img.src=`images/fun${i}.jpg`;
                divholder.appendChild(img);
            }
            pics.appendChild(divholder);

or

method2: 
let pics = document.getElementById("pics-thumbs"),
  imgArr = [];
for (let i = 1; i < 73; i++) {

  imgArr.push(`<img class="img-responsive" src="images/fun${i}.jpg">`);
}
pics.innerHTML = imgArr.join('<br>')
<div id="pics-thumbs"></div>

Savil answered 26/4, 2018 at 12:18 Comment(0)

M

0

As others pointed out if you are allowed to use a framework like jQuery the best thing to do is use it, as it high likely will do it in the best possible way. If you are not allowed to use a framework then I guess manipulating the DOM is the best way to do it (and in my opinion, the right way to do it).

Mcardle answered 23/10, 2008 at 11:14 Comment(0)

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