Tutorial by Examples: b

NaN Property of the Global Object

NaN ("Not a Number") is a special value defined by the IEEE Standard for Floating-Point Arithmetic, which is used when a non-numeric value is provided but a number is expected (1 * "two"), or when a calculation doesn't have a valid number result (Math.sqrt(-1)). Any equality or ...

JavaScript • Comparison Operations

Passing a callback function as a parameter

There are several PHP functions that accept user-defined callback functions as a parameter, such as: call_user_func(), usort() and array_map(). Depending on where the user-defined callback function was defined there are different ways to pass them: Procedural style: function square($number) { ...

PHP • Functional Programming

List Current Jobs

$ tail -f /var/log/syslog > log.txt [1]+ Stopped tail -f /var/log/syslog > log.txt $ sleep 10 & $ jobs [1]+ Stopped tail -f /var/log/syslog > log.txt [2]- Running sleep 10 &

Bash • Jobs and Processes

Job handling

Creating jobs To create an job, just append a single & after the command: $ sleep 10 & [1] 20024 You can also make a running process a job by pressing Ctrl + z: $ sleep 10 ^Z [1]+ Stopped sleep 10 Background and foreground a process To bring the Process to the f...

Bash • Jobs and Processes

Basic Random Number Generation

The function rand() can be used to generate a pseudo-random integer value between 0 and RAND_MAX (0 and RAND_MAX included). srand(int) is used to seed the pseudo-random number generator. Each time rand() is seeded wih the same seed, it must produce the same sequence of values. It should only be see...

C Language • Random Number Generation

Redirecting both STDOUT and STDERR

File descriptors like 0 and 1 are pointers. We change what file descriptors point to with redirection. >/dev/null means 1 points to /dev/null. First we point 1 (STDOUT) to /dev/null then point 2 (STDERR) to whatever 1 points to. # STDERR is redirect to STDOUT: redirected to /dev/null, # effect...

Bash • Redirection

Error objects

Runtime errors in JavaScript are instances of the Error object. The Error object can also be used as-is, or as the base for user-defined exceptions. It's possible to throw any type of value - for example, strings - but you're strongly encouraged to use Error or one of it's derivatives to ensure that...

JavaScript • Error Handling

Event Bubbling and Capturing

Events fired on DOM elements don't just affect the element they're targeting. Any of the target's ancestors in the DOM may also have a chance to react to the event. Consider the following document: <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> </hea...

DOM • Events

Downloading a file with progress information using the SwiftyDropbox library

Adapted from the tutorial, this uses the SwiftyDropbox library to download a file, with a progress callback on the download method to get progress information: // Download a file let destination : (NSURL, NSHTTPURLResponse) -> NSURL = { temporaryURL, response in let fileManager = NSFileMan...

Dropbox API • Downloading a file

Downloading a file using the Dropbox Python library

This uses the Dropbox Python SDK to download a file from the Dropbox API at the remote path /Homework/math/Prime_Numbers.txt to the local file Prime_Numbers.txt: import dropbox dbx = dropbox.Dropbox("<ACCESS_TOKEN>") with open("Prime_Numbers.txt", "wb") as f:...

Dropbox API • Downloading a file

Downloading a file with every error case handled using the SwiftyDropbox library

Dropbox.authorizedClient!.files.download(path: path, destination: destination).response { response, error in if let (metadata, url) = response { print("*** Download file ***") print("Downloaded file name: \(metadata.name)") print("Downloaded f...

Dropbox API • Downloading a file

Uploading a file from NSData with every error case handled using the SwiftyDropbox library

This uses the SwiftyDropbox library to upload a file from a NSData to the Dropbox account, using upload sessions for larger files, handling every error case: import UIKit import SwiftyDropbox class ViewController: UIViewController { // replace this made up data with the real data le...

Dropbox API • Uploading a file

Uploading a file using the Dropbox .NET library

This example uses the Dropbox .NET library to upload a file to a Dropbox account, using upload sessions for larger files: private async Task Upload(string localPath, string remotePath) { const int ChunkSize = 4096 * 1024; using (var fileStream = File.Open(localPath, FileMode.Open)) ...

Dropbox API • Uploading a file

Getting account information using the Dropbox Python library

This uses the Dropbox Python SDK to get the user's account information from the Dropbox API. import dropbox dbx = dropbox.Dropbox("<ACCESS_TOKEN>") dbx.users_get_current_account() <ACCESS_TOKEN> should be replaced with the access token.

Dropbox API • Getting account information

Sharing a folder with every error case handled using the SwiftyDropbox library

This uses the SwiftyDropbox library to share a folder, handling every error case: Dropbox.authorizedClient!.sharing.shareFolder(path: "/folder_path").response { response, error in if let result = response { print("response: \(result)") } else if let callError ...

Dropbox API • Sharing a folder

Inviting a member to a shared folder using curl

curl -X POST https://api.dropboxapi.com/2/sharing/add_folder_member \ --header "Authorization: Bearer <ACCESS_TOKEN>" \ --header "Content-Type: application/json" \ --data "{\"shared_folder_id\": \"<SHARED_FOLDER_ID\",\"members...

Dropbox API • Sharing a folder

Inviting a member to a shared folder with every error case handled using the SwiftyDropbox library

let toInvite = [Sharing.AddMember(member: Sharing.MemberSelector.Email("<EMAIL_ADDRESS_TO_INVITE>"))] Dropbox.authorizedClient!.sharing.addFolderMember(sharedFolderId: "<SHARED_FOLDER_ID>", members: toInvite).response { response, error in if (response != nil...

Dropbox API • Sharing a folder

Listing the root folder using the SwiftyDropbox library, distinguishing files and folders in the response

Dropbox.authorizedClient!.files.listFolder(path: "").response { response, error in print("*** List folder ***") if let result = response { print("Folder contents:") for entry in result.entries { print(entry.name) if ...

Dropbox API • Listing a folder

Attempting to list a non-existant folder using the SwiftyDropbox library, as an example of error handling

// List folder Dropbox.authorizedClient!.files.listFolder(path: "/nonexistantpath").response { response, error in print("*** List folder ***") if let result = response { print("Folder contents:") for entry in result.entries { pr...

Dropbox API • Listing a folder

Get file metadata for a file, including media information, using the SwiftyDropbox library

Dropbox.authorizedClient!.files.getMetadata(path: "/test.jpg", includeMediaInfo: true).response { response, error in if let result = response as? Files.FileMetadata { print(result.name) if result.mediaInfo != nil { switch result.mediaInfo! as Files.Med...

Dropbox API • Getting file metadata