First, we define a squareImages filter function for filtering images in the collection with equal width and height. Next, we define a collectionToCSV higher-order function which takes an array of keys and returns a function that takes an array collection of objects and converts it to a CSV string extracting only the specified keys from each object.
Finally, we specify the fields we want to extract from each photo object in the collection in the exportFields array. Here is what the output could look like on the console:. In this example, we will use the Canvas API to manipulate the pixels of an image, making it appear grayscale.
Here is a comparison between an actual image and the corresponding grayscale canvas image. You can learn about Blobs here. Blobs are objects that are used to represent raw immutable data.
Blob objects store information about the type and size of data they contain, making them very useful for storing and working file contents on the browser. In fact, the File object is a special extension of the Blob interface. Blob objects can be obtained from a couple of sources:.
Here are some code samples for the aforementioned blob object sources:. It is one thing to obtain a blob object and another thing altogether to work with it. One thing you want to be able to do is to read the content of the blob.
That sounds like a good opportunity to use a FileReader object. You can learn about FileReader objects here. A FileReader object provides some very helpful methods for asynchronously reading the content of blob objects or files in different ways. The FileReader interface has pretty good browser support and supports reading blob data as follows as at the time of this writing :. Here is what a typical object URL looks like:.
The URL. Here is what it looks like:. It is important to note that, this method will always return a new object URL each time it is called, even if it is called with the same blob object.
Read More From Actual Wizard Understanding the Different Parts of an Email Address An email address has four parts; the recipient name, the symbol, the domain name, and the top-level domain.
There are a number of different ways to get the last element of an array in JavaScript. Below we will explore …. How to use document. Opening a new browser window in a new tab can be done easily in JavaScript. You want to allow the end user to download the canvas content as an image file.
How would you do that? The download attribute along with data URLs can be used to accomplish this task. Let's see how. The download hyperlink placed below the canvas allows you to download the canvas graphics. The Download JavaScript function is responsible for doing this job for us.
It is shown below :. The Download function first draws a rectangle on the canvas and then clears a region from the rectangle. We won't go into any details of canvas element here. Then we grab the reference to the download anchor element and set its href and download properties. The href property is set to a data URLntaining the base64 encoded e data. This is done using the toDataURL method of the canvas. The download property is set to MyCanvas. Another use of the download attribute could be when you want the user to download dynamically generated CSV or XML data.
Suppose you have a table displayed on a web page like this :. You can accomplish this task with a dash of jQuery code as shown below :. The above code wires the click event handler of the Download Table link. Upon clicking the link the code converts the table data into CSV. This is done using a jQuery plugin - table2CSV.
We grab the data in a variable. Moreover, we also set the download property of the hyperlink to EmployeeTable. This way the download dialog will have the default file name of EmployeeTable. Online Courses ASP. The download attribute introduced in HTML5 comes handy in the following situations : You want the user to download a resource rather than navigating to it.
You want to assign some default file name for the file being downloaded. Note that the download attribute works only for same origin URLs.
Let's try to use the download attribute in a simple ASP. The opens a new tab but downloads the file and closes the tab once it realizes it's not a file type it should render. In my case it was a.
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