-
Notifications
You must be signed in to change notification settings - Fork 22.5k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
Showing
12 changed files
with
163 additions
and
18 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,141 @@ | ||
| --- | ||
| title: "javascript: URLs" | ||
| slug: Web/URI/Schemes/javascript | ||
| page-type: guide | ||
| spec-urls: https://html.spec.whatwg.org/multipage/browsing-the-web.html#the-javascript:-url-special-case | ||
| --- | ||
|
|
||
| {{QuickLinksWithSubpages("/en-US/docs/Web/URI")}} | ||
|
|
||
| > [!WARNING] | ||
| > Using `javascript:` URLs on the web is discouraged as it may lead to execution of arbitrary code, similar to the ramifications of using [`eval()`](/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval). It may also be inaccessible because it deviates from normal link behavior. | ||
| `javascript:` URLs, URLs prefixed with the `javascript:` scheme, are used as if they were a kind of navigation target but actually executes JavaScript when the browser goes to the target location. | ||
|
|
||
| ## Syntax | ||
|
|
||
| `javascript:` URLs start with the `javascript:` scheme and are followed by JavaScript code. The code will be parsed as a script. | ||
|
|
||
| ```url | ||
| javascript:<script> | ||
| ``` | ||
|
|
||
| ## Description | ||
|
|
||
| `javascript:` URLs can be used anywhere a URL is a navigation target. This includes, but is not limited to: | ||
|
|
||
| - The [`href`](/en-US/docs/Web/HTML/Element/a#href) attribute of an `<a>` or `<area>` element. | ||
| - The [`action`](/en-US/docs/Web/HTML/Element/form#action) attribute of a `<form>` element. | ||
| - The [`src`](/en-US/docs/Web/HTML/Element/iframe#src) attribute of an `<iframe>` element. | ||
| - The [`window.location`](/en-US/docs/Web/API/Window/location) JavaScript property. | ||
|
|
||
| > [!NOTE] | ||
| > Some other contexts that use URLs, such as the [`href`](/en-US/docs/Web/HTML/Element/link#href) attribute of `<link>` elements, do not allow `javascript:` URLs, because they are resource locations, not navigation targets. For these cases, if you want to write JavaScript inline, use [`data:`](/en-US/docs/Web/URI/Schemes/data) URLs with the `text/javascript` MIME type. | ||
| When a browser attempts to navigate to such a location, it parses and executes the script body. The script may have a _completion value_ (not a return value), which is the same value if the script were executed with [`eval()`](/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval). If the last statement is an [expression](/en-US/docs/Web/JavaScript/Reference/Statements/Expression_statement), the completion value is the value of that expression. If this completion value is a string, that string is treated as an HTML document and the browser navigates to a new page with that content, using the same URL as the current page. If the completion value is not a string, the browser only executes the code and does not navigate. Therefore, it's often recommended that if the script ends with a function call like `javascript:foo()`, you should prefix it with {{jsxref("Operators/void", "void")}} to prevent accidental navigation if the function happens to return a string. | ||
|
|
||
| `javascript:` navigation may be blocked by [content security policy](/en-US/docs/Web/HTTP/CSP) settings, in particular {{CSP("script-src")}}. | ||
|
|
||
| ## Examples | ||
|
|
||
| ### Using `javascript:` URLs as href targets | ||
|
|
||
| In this example, the `href` attribute of an `<a>` element is set to a `javascript:` URL that alerts a message when clicked: | ||
|
|
||
| ```html example-bad | ||
| <a href="javascript:alert('Hello, world!')">Click me</a> | ||
| ``` | ||
|
|
||
| Because {{domxref("Window/alert", "alert()")}} returns `undefined`, the browser does not navigate to a new page. This is a bad practice because the link is actually not a hyperlink. Consider making it a button instead: | ||
|
|
||
| ```html example-good | ||
| <button id="btn">Click me</button> | ||
| <script> | ||
| document.getElementById("btn").addEventListener("click", () => { | ||
| alert("Hello, world!"); | ||
| }); | ||
| </script> | ||
| ``` | ||
|
|
||
| In this example, the `href` attribute of an `<a>` element is set to a `javascript:` URL that navigates to a new page with the content "Hello, world!": | ||
|
|
||
| ```html | ||
| <a href="javascript:pageContent">Click me</a> | ||
| <script> | ||
| // Use a var so it becomes a global variable and can be read elsewhere | ||
| var pageContent = "Hello, world!"; | ||
| </script> | ||
| ``` | ||
|
|
||
| Note that because `javascript:` URLs do not create history entries, there's no way to go back to the previous page without refreshing. | ||
|
|
||
| ### Using `javascript:` URLs as form actions | ||
|
|
||
| In this example, the `action` attribute of a `<form>` element is set to a `javascript:` URL that alerts a message when submitted: | ||
|
|
||
| ```html example-bad | ||
| <form action="javascript:alert(myInput.value)"> | ||
| <input id="myInput" /> | ||
| <input type="submit" value="Submit" /> | ||
| </form> | ||
| ``` | ||
|
|
||
| Instead of doing this, consider listening for the form's `submit` event and handling it with JavaScript: | ||
|
|
||
| ```html | ||
| <form id="myForm"> | ||
| <input id="myInput" /> | ||
| <input type="submit" value="Submit" /> | ||
| </form> | ||
| <script> | ||
| document.getElementById("myForm").addEventListener("submit", (event) => { | ||
| event.preventDefault(); | ||
| alert(document.getElementById("myInput").value); | ||
| }); | ||
| </script> | ||
| ``` | ||
|
|
||
| ### Using `javascript:` URLs as iframe sources | ||
|
|
||
| In this example, the `src` attribute of an `<iframe>` element is set to a `javascript:` URL that navigates to a new page with the content "Hello, world!": | ||
|
|
||
| ```html | ||
| <iframe src="javascript:pageContent"></iframe> | ||
| <script> | ||
| // Use a var so it becomes a global variable and can be read elsewhere | ||
| var pageContent = "Hello, world!"; | ||
| </script> | ||
| ``` | ||
|
|
||
| Instead of doing this, consider setting the `srcdoc` attribute instead: | ||
|
|
||
| ```html | ||
| <iframe id="myFrame"></iframe> | ||
| <script> | ||
| document.getElementById("myFrame").srcdoc = "Hello, world!"; | ||
| </script> | ||
| ``` | ||
|
|
||
| ### Using `javascript:` URLs with window.location | ||
|
|
||
| In this example, the `window.location` property is set to a `javascript:` URL that navigates to a new page with the content "Hello, world!": | ||
|
|
||
| ```js example-bad | ||
| window.location = "javascript:'Hello world!'"; | ||
| ``` | ||
|
|
||
| Instead of doing this, consider using [DOM APIs](/en-US/docs/Web/API/HTML_DOM_API) to modify the page content. For example: | ||
|
|
||
| ```js example-good | ||
| document.body.textContent = "Hello, world!"; | ||
| ``` | ||
|
|
||
| ## Specifications | ||
|
|
||
| {{Specifications}} | ||
|
|
||
| ## See also | ||
|
|
||
| - [URIs](/en-US/docs/Web/URI) | ||
| - [Content Security Policy (CSP)](/en-US/docs/Web/HTTP/CSP) | ||
| - [IANA list of URI schemes](https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml) |