ChatGPT解决这个技术问题 Extra ChatGPT

How to trigger a file download when clicking an HTML button or JavaScript

This is crazy but I don't know how to do this, and because of how common the words are, it's hard to find what I need on search engines. I'm thinking this should be an easy one to answer.

I want a simple file download, that would do the same as this:

<a href="file.doc">Download!</a>

But I want to use an HTML button, e.g. either of these:

<input type="button" value="Download!">
<button>Download!</button>

Likewise, is it possible to trigger a simple download via JavaScript?

$("#fileRequest").click(function(){ /* code to download? */ });

I'm definitely not looking for a way to create an anchor that looks like a button, use any back-end scripts, or mess with server headers or mime types.

Thanks to you "how to trigger a file download in javascript" would give answers much faster for any future searcher.
Your restrictions in your final paragraph don't make much sense to me. If you're open to answers that use JavaScript (since you say so) or that require changing the DOM structure (like the one you've accepted), why not also an anchor styled as a button? I can't imagine a scenario where the first two would be fine but the anchor as a button would be problematic.

M
MultiplyByZer0

You can trigger a download with the HTML5 download attribute.

<a href="path_to_file" download="proposed_file_name">Download</a>

Where:

path_to_file is a path that resolves to an URL on the same origin. That means the page and the file must share the same domain, subdomain, protocol (HTTP vs. HTTPS), and port (if specified). Exceptions are blob: and data: (which always work), and file: (which never works).

proposed_file_name is the filename to save to. If it is blank, the browser defaults to the file's name.

Documentation: MDN, HTML Standard on downloading, HTML Standard on download, CanIUse


Not Work With Safari and certain IE versions
Using a combination of download and target="_blank" seems to be sufficient to cover most use cases. Browsers that understand download treat it as a download, otherwise it's opened in a new tab.
How can this be applied to a button object instead of just an a tag?
Actually this only works for urls of the same origin as mentioned in the MDN docs. This is a huge limitation if we are looking to develop a generic solution
The question is explicitly asking to use a button instead of a link
G
Gray

For the button you can do

<form method="get" action="file.doc">
   <button type="submit">Download!</button>
</form>

doesn't work as a trigger, just redirect to the url as 'a' tag.
This works better : Download
@kscius even today the download attribute is not supported in IE 11 (it is now supported in Edge) and it is not supported in Safari. In 2012 when the answer was originally posted it wasn't supported in any major browser.
what's the difference between having an anchor with button styling and having a form with a button?
This doesn't necessarily trigger a download. It simply causes the browser to navigate to file.doc. Whether that results in file.doc being downloaded or being shown as a page in the browser depends upon the headers returned by the server when it serves file.doc and on what file types the browser is capable of rendering.
A
Ani Menon

HTML:

<button type="submit" onclick="window.open('file.doc')">Download!</button>

What if i wanna download a xml file?
Thanks for your code. I have tested, it can working in IE, Chrome, Firefox.
If you have a file acceptable by the browser like a PDF it will open in new tab instead to show download dialog.
window.open can trigger popup-blocking in a browser and is thus not recommended. You could use window.location = 'path' , although that would go to the location in the same browser window.
This doesn't necessarily trigger a download. It simply causes the browser to navigate to file.doc. Whether that results in file.doc being downloaded or being shown as a page in the browser depends upon the headers returned by the server when it serves file.doc and on what file types the browser is capable of rendering.
s
syntagma

A simple JS solution:

function download(url) {
  const a = document.createElement('a')
  a.href = url
  a.download = url.split('/').pop()
  document.body.appendChild(a)
  a.click()
  document.body.removeChild(a)
}

@NicholasKyriakides Kind of reminds me of this gem: image.ibb.co/dtkUWJ/Selection_002.png
@BryanLarsen You are right, Firefox doesn't allow this without adding the element to body first. Thank you, updating the answer
Is there a way that javascript function be triggered once the download finishes? Just trying to show a message once downloads start and remove the message once download completes.
@mohitbansal (un)fortunately no as it's in the browser level
This is best solution out here and should be accepted answer.
M
Mark Amery

With jQuery:

$("#fileRequest").click(function() {
    // hope the server sets Content-Disposition: attachment!
    window.location = 'file.doc';
});

Perfect, thanks. Do you happen to know if most servers will set the Content-Disposition to 'attachment' by default?
There is no "most." It completely depends. Don't rely on it being set.
This issue has been driving me ballistic, and this was the only option that worked (and is supported by IE). I'll add for any n00bs like me that to set the Content-Disposition, all you have to do is:
No jquery. Period.
This doest work if you're trying to download an image, it would open the image in the browser
D
Danubian Sailor

You can do it with "trick" with invisible iframe. When you set "src" to it, browser reacts as if you would click a link with the same "href". As opposite to solution with form, it enables you to embed additional logic, for example activating download after timeout, when some conditions are met etc.

It is also very silient, there's no blinking new window/tab like when using window.open.

HTML:

<iframe id="invisible" style="display:none;"></iframe>

Javascript:

function download() {
    var iframe = document.getElementById('invisible');
    iframe.src = "file.doc";
}

It does, at least if you actually apprnf the iframe to document.body.
This doesn't seem to be working in Chrome right now, although it used to work. I wonder if it kind of intermittently stops working in different versions of Chrome.
Works in Chrome as of Version 61.0.3163.100 (Official Build) (64-bit)
Does not work with images in Firefox v57. It just renders the image in the iframe.
This will fail silently if the file is of a type the browser knows how to render itself, though (unless the server returns a Content-Disposition header indicating the file should be downloaded).
g
georgeawg

Bootstrap Version

<a class="btn btn-danger" role="button" href="path_to_file"
   download="proposed_file_name">
  Download
</a>

Documented in Bootstrap 4 docs, and works in Bootstrap 3 as well.


The only thing this has to do with Bootstrap is the class names, it's just the power of HTML5.
The question is explicitly asking how to do this with a button instead of a link.
if you knew anything at all about bootstrap, you would see that it IS a button.
The button tag didn't work for me. But this one did.
D
Delconis

I think this is the solution you were looking for

<button type="submit" onclick="window.location.href='file.doc'">Download!</button>

I hade a case where my Javascript generated a CSV file. Since there is no remote URL to download it I use the following implementation.

downloadCSV: function(data){
    var MIME_TYPE = "text/csv";

    var blob = new Blob([data], {type: MIME_TYPE});
    window.location.href = window.URL.createObjectURL(blob);
}

on 404 -> page change to a 404 error page. same problem as stated on the other location.href solutions.
This (at least the first implementation) doesn't necessarily trigger a download. It simply causes the browser to navigate to file.doc. Whether that results in file.doc being downloaded or being shown as a page in the browser depends upon the headers returned by the server when it serves file.doc and on what file types the browser is capable of rendering.
S
Starwarswii

You can hide the download link and make the button click it.

<button onclick="document.getElementById('link').click()">Download!</button>
<a id="link" href="file.doc" download hidden></a>

For this to work in Firefox, the resource has to be on the same domain as the document. Setting CORS headers does not help.
Don't ever do this
J
John Weisz

What about:

<input type="button" value="Download Now!" onclick="window.location = 'file.doc';">

This does not work, if your file, for example, is an image, since it would just be opened in the browser.
Another issue occurs which is if the file is missing it navigates the entire page to a 404 page
It works perfectly in 2020 (for every file), and it is the simplest solution of all. Amazing!
This doesn't necessarily trigger a download. It simply causes the browser to navigate to file.doc. Whether that results in file.doc being downloaded or being shown as a page in the browser depends upon the headers returned by the server when it serves file.doc and on what file types the browser is capable of rendering.
J
Juca Duarte

Hello I just include the word 'download' and works well.

<a href="file.pdf" download>Download</a>

So in javascript you can use the follow:

function onStartedDownload(id) {
  console.log(`Started downloading: ${id}`);
}

function onFailed(error) {
  console.log(`Download failed: ${error}`);
}

var downloadUrl = "https://example.org/image.png";

var downloading = browser.downloads.download({
  url : downloadUrl,
  filename : 'my-image-again.png',
  conflictAction : 'uniquify'
});

downloading.then(onStartedDownload, onFailed);

Uncaught ReferenceError: browser is not defined
D
David Willhite

If your looking for a vanilla JavaScript (no jQuery) solution and without using the HTML5 attribute you could try this.

const download = document.getElementById("fileRequest"); download.addEventListener('click', request); function request() { window.location = 'document.docx'; } .dwnld-cta { border-radius: 15px 15px; width: 100px; line-height: 22px }

Download File


This doesn't necessarily trigger a download. It simply causes the browser to navigate to file.doc. Whether that results in file.doc being downloaded or being shown as a page in the browser depends upon the headers returned by the server when it serves file.doc and on what file types the browser is capable of rendering.
S
Suragch

In my testing the following works for all file types and browsers as long as you use a relative link:

<a href="/assets/hello.txt" download="my_file.txt"><button>Download 2</button></a>

/assets/hello.txt is just a relative path on my site. Change it to your own relative path.

my_file.txt is the name you want the file to be called when it is downloaded.

Explanation

I noticed there were comments under a lot of the answers that said the browser would just try to open the file itself rather than downloading it depending on the file type. I discovered this to be true.

I made two buttons to test it out using two different methods:

https://i.stack.imgur.com/1lmuI.png

<button onclick="window.location.href='/assets/hello.txt';">Download 1</button>

<a href="/assets/hello.txt" download="my_file.txt"><button>Download 2</button></a>

Notes:

Button 1 opened the text file in a new browser tab. However, Button 1 would download the file for file types that it couldn't open itself (for example, .apk files).

Button 2 downloaded the text file. However, Button 2 only downloaded the file if the path was relative. When I changed the path to an absolute path, then the browser opened it in a new tab.

I tested this on Firefox, Safari, and Chrome.


J
John Weisz

Anywhere between your <body> and </body> tags, put in a button using the below code:

<button>
    <a href="file.doc" download>Click to Download!</a>
</button>

This is sure to work!


For Chrome it is a great solution
Doesn't work in Safari either: W3 Schools
Not working in the MS browsers is a rather big problem and Chrome is not always going to be the answer.
You can't put a link inside a button in HTML
Not legal HTML; validator.w3.org/nu complains that "The element a must not appear as a descendant of the button element." Seems to render nonetheless in the browsers I've tried, but all the same, I wouldn't risk it.
s
slayernoah

This is what finally worked for me since the file to be downloaded was determined when the page is loaded.

JS to update the form's action attribute:

function setFormAction() {
    document.getElementById("myDownloadButtonForm").action = //some code to get the filename;
}

Calling JS to update the form's action attribute:

<body onLoad="setFormAction();">

Form tag with the submit button:

<form method="get" id="myDownloadButtonForm" action="">
    Click to open document:  
    <button type="submit">Open Document</button>
</form>

The following did NOT work:

<form method="get" id="myDownloadButtonForm" action="javascript:someFunctionToReturnFileName();">

probably because if you have the file at load time, can't you just render the action on the server using a templating engine? why the need for js code?
Like other solutions here that use a default form action, this doesn't necessarily trigger a download. It simply causes the browser to navigate to the target URL. Whether that results in the file at that URL being downloaded or being shown as a page in the browser depends upon the headers returned by the server when it serves the file and on what file types the browser is capable of rendering.
M
Mark Amery

If you can't use form, another approach with downloadjs fit nice. Downloadjs use blob and html 5 file API under the hood:

<div onClick=(()=>{downloadjs(url, filename)})/>

*it's jsx/react syntax, but can be used in pure html


To avoid CORS problems for images on other domains, put crossorigin="anonymous" into the img tag, like this:
I had a button that would download an in-memory string as a file. This worked, no problems. Thanks.
m
m24197

<a href="file.doc"><button>Download!</button></a>
This will download the file as .doc file extension is not supported to be opened in browser.
One of the simplest way for button and the text-decoration will help to alter or to remove the text decoration of the link.


Simplest solution ever.
S
Sebi Nechita

Not really an answer to the original question but it may help others which face similar situations as myself.

If the file you want to download is not hosted on the same origin but you want to be able to download it, you can do that with the Content-Disposition header. Make sure the server includes the header when responding to requests of the file.

Setting a value like Content-Disposition: attachment will ensure that the file will be downloaded instead of viewed in the browser.

A simple <a href="http://www.notMyOrigin.com/file.txt">Download</a> pointing to your file should download it in this case.


R
RKM

If you want

<a href="path_to_file" download="proposed_file_name">Download</a>

for the ability to download files that would be rendered by the browser otherwise, But still want a neat javascript function to use in a button; you can have an invisible link in html and click it in javascript.

function download_file() { document.getElementById("my_download").click() }


M
Mostafa Ghorbani

all you need to do is add Download after the file name which you have entered:

Before:

<a href="file.doc">Download!</a>

After

<a href="file.doc" Download >Download!</a>

Make sure the download is written with a capital letter otherwise it's not gonna work.


B
BananaAcid

Another way of doing in case you have a complex URL such as file.doc?foo=bar&jon=doe is to add hidden field inside the form

<form method="get" action="file.doc">
  <input type="hidden" name="foo" value="bar" />
  <input type="hidden" name="john" value="doe" />
  <button type="submit">Download Now</button>
</form>

inspired on @Cfreak answer which is not complete


s
sourabh sharma

The solution I have come up with is that you can use download attribute in anchor tag but it will only work if your html file is on the server. but you may have a question like while designing a simple html page how can we check that for that you can use VS code live server or bracket live server and you will see your download attribute will work but if you will try to open it simply by just double clicking html page it open the file instead of downloading it. conclusion: attribute download in anchor tag only works if your html file is no server.


B
Brana

For me ading button instead of anchor text works really well.

<a href="file.doc"><button>Download!</button></a>

It might not be ok by most rules, but it looks pretty good.


This only works because your browser doesn't support .doc files.
Your HTML is invalid. <a> elements may not contain <button> elements.
was it always that way though? This answer was two years old when you commented that.
J
John Weisz

If you use the <a> tag, do not forget to use the entire url which leads to the file -- i.e.:

<a href="http://www.example.com/folder1/file.doc">Download</a>

I don't think that's the problem here. Also the "absolute" path isn't needed if the link is in the same path as the file.
@Rocket - you are, of course, correct about the absolute path, however, it is the best way to make certain to get it right. I will leave it to the OP to decide if it was helpful -
The question is explicitly asking how to do this with a button instead of a link.
the download attribute is missing in this solution. Even after adding download attributes it will not work for cross-domain.