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HomeSoftware EngineeringDiscover Clipboard Operation in JavaScript | by Sabesan Sathananthan | Geek Tradition

Discover Clipboard Operation in JavaScript | by Sabesan Sathananthan | Geek Tradition

Reduce, Copy and Paste in JavaScript

The browser permits JavaScript scripts to learn and write to the clipboard, and mechanically copy or paste content material. Typically, scripts mustn’t modify the person’s clipboard, in order to not meet the person’s expectations. Nevertheless, typically it may be handy to do that, such because the “one-click copy” operate, the person clicks a button, and the required content material is mechanically entered into the clipboard. At present, there are 3 ways to implement clipboard operations.

  • Doc.execCommand()technique
  • Asynchronous Clipboard API
  • copy,reduce and paste Occasions

This text introduces these three strategies one after the other. That is my thirty seventh Medium article.

Doc.execCommand() is the standard technique of manipulating the clipboard, which is supported by numerous browsers. It helps the three operations of copy, reduce, and paste.

  • Doc.execCommand('copy') — copy
  • Doc.execCommand('reduce') — reduce
  • Doc.execCommand('paste') — paste

Copy or Reduce operation

When copying, first choose the textual content after which name the Doc.execCommand('copy'), the chosen textual content will enter the clipboard.

Within the above instance, the script first selects the textual content within the inputElement of the enter field ( inputElement.choose() ), after which Doc.execCommand('copy') copies it to the clipboard. Observe that the copy operation is greatest positioned within the occasion listener operate, triggered by the person (for instance, the person clicks a button). If the script is executed autonomously, some browsers could report an error. Reduce operation can be much like the copy operation.

Paste operation

When pasting, calling Doc.execCommand('paste') will output the contents of the clipboard to the present focus factor.


Though the Doc.execCommand() technique is handy, it has some disadvantages. First, it will possibly solely copy the chosen content material to the clipboard, and can’t write content material to the clipboard arbitrarily. Secondly, it’s an asynchronous operation. If you happen to copy/paste a considerable amount of information, the web page will freeze. Some browsers will even pop up a immediate field and ask the person for permission. Right now, the web page will change into unresponsive earlier than the person makes a alternative. So as to remedy these issues, browser distributors have proposed an asynchronous Clipboard API.

Clipboard API is the next-generation clipboard operation technique, which is extra highly effective and affordable than the standard Doc.execCommand() technique. All its operations are asynchronous and return Promise objects with out inflicting web page jams. Furthermore, it will possibly put arbitrary content material (resembling photos) into the clipboard. The navigator.clipboard property returns the Clipboard object, and all operations are carried out by this object.

const clipboardObj = navigator.clipboard;

If the navigator.clipboard property returns undefined, it signifies that the present browser doesn’t help this API (you possibly can see the complete compatibly desk on Can I take advantage of…). Since customers could put delicate information (resembling passwords) on the clipboard, permitting scripts to learn them arbitrarily will trigger safety dangers, so this API has extra safety restrictions. To start with, the Chrome browser stipulates that solely HTTPS protocol pages can use this API. Nevertheless, the event setting (localhost) permits using non-encrypted protocols. Secondly, the person’s permission must be clearly obtained when calling. The precise implementation of permissions makes use of the Permissions API. There are two permissions associated to the clipboard: clipboard-write (write permission) and clipboard-read (learn permission). The “write permission” is mechanically granted to the script, and the “learn permission” should be explicitly granted by the person. In different phrases, the script may be mechanically accomplished when writing to the clipboard, however when studying the clipboard, the browser will pop up a dialog field asking whether or not the person agrees to learn.

As well as, it needs to be famous that what the script reads is at all times the clipboard of the present web page. One drawback that this brings is that in case you paste the related code into the developer instrument and run it instantly, an error could also be reported as a result of the present web page presently is the window of the developer instrument, not an online web page.

If you happen to paste the above code into the developer instrument and run it, an error will probably be reported. As a result of when the code is operating, the developer instrument window is the present web page, and there’s no DOM interface that the Clipboard API depends upon this web page. One resolution is to place the related code in setTimeout() to delay operating, and rapidly click on on the web page window of the browser earlier than calling the operate to show it into the present web page.

After the above code is pasted into the developer instrument to run, rapidly click on on the web page window of the webpage to make it the present web page, in order that no error will probably be reported.

Clipboard object


The clipboard.readText() technique is used to repeat the textual content information within the clipboard.

Within the above instance, after the person clicks on the web page, the textual content within the clipboard will probably be output. Observe that the browser will pop up a dialog field presently, asking the person whether or not to agree with the script to learn the clipboard.

If the person disagrees, the script will report an error. Right now, you need to use the strive...catch construction to deal with errors.


The clipboard.learn() technique is used to repeat the info within the clipboard, which may be textual content information or binary information (resembling photos). This technique requires express permission from the person. This technique returns a Promise object. As soon as the state of the item turns into resolved, an array may be obtained, and every array member is an occasion of a ClipboardItem object.

The ClipboardItem object represents a single clip merchandise and every clip merchandise has a clipboardItem.sorts property and a clipboardItem.getType() technique. The clipboardItem.sorts property returns an array whose members are the MIME sorts obtainable for the clip merchandise. For instance, a clip merchandise may be pasted in HTML format or in plain textual content format. Then it has two MIME sorts (textual content/html and textual content/plain). The clipboardItem.getType(sort) technique is used to learn the info of the clip merchandise and returns a Promise object. This technique accepts the MIME sort of the clip merchandise as a parameter and returns the info of that sort. This parameter is required, in any other case, an error will probably be reported.


The clipboard.writeText() technique is used to jot down textual content content material to the clipboard.

The above instance is that after the person clicks on the net web page, the script writes textual content information to the clipboard. This technique doesn’t require person permission, however it’s best to place it in strive...catch to forestall errors.


The clipboard.write() technique is used to jot down arbitrary information to the clipboard, which may be textual content information or binary information. This technique accepts a ClipboardItem occasion as a parameter, which represents the info written to the clipboard.

Within the above instance, the script writes an image to the clipboard. Observe that the Chrome browser at present (till this author writes this text) solely helps writing pictures in PNG format. clipboardItem() is a constructor natively supplied by the browser to generate an occasion of clipboardItem. It accepts an object as a parameter. The important thing identify of the item is the MIME sort of the info, and the important thing worth is the info itself. The next instance is to jot down the worth of the identical clip merchandise in a number of codecs to the clipboard, one is textual content information, and the opposite is binary information for pasting on totally different events.

When the person places information into the clipboard, the copy occasion will probably be triggered. The next instance is to transform the textual content that the person places on the clipboard to uppercase.

Within the above instance, the clipboardData property of the occasion object accommodates the clipboard information. It’s an object with the next properties and strategies.

  • Occasion.clipboardData.setData(sort, information) : To switch the clipboard information, you want to specify the info sort.
  • Occasion.clipboardData.getData(sort) : To acquire clipboard information, you want to specify the info sort.
  • Occasion.clipboardData.clearData([type]) : Clear clipboard information, you possibly can specify the info sort. If you don’t specify the kind, all forms of information will probably be cleared.
  • Occasion.clipboardData.gadgets : An array-like object accommodates all clip gadgets, however often there is just one clip merchandise

The next instance is to intercept the person’s copy operation and put the required content material into the clipboard.

Within the above instance, first, use e.preventDefault() to cancel the default operation of the clipboard, after which the script takes over the copy operation. The reduce occasion is triggered when the person performs a reducing operation. Its processing is precisely the identical because the copy occasion, and the reduce information can be obtained from the Occasion.clipboardData property.

When the person makes use of the clipboard information to stick, the paste occasion will probably be triggered. The next instance is to intercept the paste operation, the info within the clipboard is taken out by the script.



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