Requires that every update to the file's content be written synchronously to the underlying storage device.
This option is primarily intended for use with work files that are used solely by a single instance of the Java virtual machine. This option is not recommended for use when opening files that are open concurrently by other entities. Many of the details as to when and how the file is deleted are implementation specific and therefore not specified.
In particular, an implementation may be unable to guarantee that it deletes the expected file when replaced by an attacker while the file is open. Consequently, security sensitive applications should take care when using this option. For security reasons, this option may imply the LinkOption.
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The Referrer and Referer fields are interchangeable. If the request has no body, returns null. For more information, or if you have issues or concerns, see type-is.
Optionally, you can specify defaultValue to set a default value if the parameter is not found in any of the request objects. Direct access to req. Body-parsing middleware must be loaded for req. Otherwise, this property is identical to app. This property is useful for exposing request-level information such as the request path name, authenticated user, user settings, and so on.
Appends the specified value to the HTTP response header field. If the header is not already set, it creates the header with the specified value.
The value parameter can be a string or an array. If a filename is given, then it sets the Content-Type based on the extension name via res. Sets cookie name to value. The value parameter may be a string or object converted to JSON. Any option not specified defaults to the value stated in RFC The encode option allows you to choose the function used for cookie value encoding.
Does not support asynchronous functions. You need to set a domain-wide cookie for another site in your organization. This other site not under your administrative control does not use URI-encoded cookie values.
The following is equivalent to the second example above. You can pass an object as the value parameter; it is then serialized as JSON and parsed by bodyParser middleware. When using cookie-parser middleware, this method also supports signed cookies. Simply include the signed option set to true. Later you may access this value through the req. Clears the cookie specified by name.
For details about the options object, see res. Web browsers and other compliant clients will only clear the cookie if the given options is identical to those given to res.
Typically, browsers will prompt the user for download. Override this default with the filename parameter. When an error occurs or transfer is complete, the method calls the optional callback function fn. This method uses res. The optional options argument passes through to the underlying res. Ends the response process. This method actually comes from Node core, specifically the response. Use to quickly end the response without any data. If you need to respond with data, instead use methods such as res.
If the header is not specified, the first callback is invoked. The Content-Type response header is set when a callback is selected. However, you may alter this within the callback using methods such as res. In addition to canonicalized MIME types, you may also use extension names mapped to these types for a slightly less verbose implementation:.
Sends a JSON response. This method is identical to res. Override this with the jsonp callback name setting. Redirects to the URL derived from the specified path , with specified status , a positive integer that corresponds to an HTTP status code. Redirects can be relative to the root of the host name. For example, if the application is on http: Redirects can be relative to the current URL.
For example, from http: If you found the above behavior confusing, think of path segments as directories with trailing slashes and files, it will start to make sense. Path-relative redirects are also possible. If you were on http: Renders a view and sends the rendered HTML string to the client. The view argument is a string that is the file path of the view file to render.
This can be an absolute path, or a path relative to the views setting. If the path does not contain a file extension, then the view engine setting determines the file extension.
For more information, see Using template engines with Express. The view argument performs file system operations like reading a file from disk and evaluating Node. The local variable cache enables view caching. Set it to true , to cache the view during development; view caching is enabled in production by default. The body parameter can be a Buffer object, a String , an object, or an Array. This method performs many useful tasks for simple non-streaming responses: Transfers the file at the given path.
Unless the root option is set in the options object, path must be an absolute path to the file. This API provides access to data on the running file system. Ensure that either a the way in which the path argument was constructed into an absolute path is secure if it contains user input or b set the root option to the absolute path of a directory to contain access within. When the root option is provided, the path argument is allowed to be a relative path, including containing..
Express will validate that the relative path provided as path will resolve within the given root option. The method invokes the callback function fn err when the transfer is complete or when an error occurs.
If the callback function is specified and an error occurs, the callback function must explicitly handle the response process either by ending the request-response cycle, or by passing control to the next route. The following example illustrates using res. For more information, or if you have issues or concerns, see send. Sets the response HTTP status code to statusCode and send its string representation as the response body.
If an unsupported status code is specified, the HTTP status is still set to statusCode and the string version of the code is sent as the response body. Some versions of Node. To set multiple fields at once, pass an object as the parameter. Sets the HTTP status for the response. A router object is an isolated instance of middleware and routes.
Every Express application has a built-in app router. A router behaves like middleware itself, so you can use it as an argument to app. The top-level express object has a Router method that creates a new router object. You can then use a router for a particular root URL in this way separating your routes into files or even mini-apps.
This method is just like the router. For example, if you placed the following route at the top of all other route definitions, it would require that all routes from that point on would require authentication, and automatically load a user.
Keep in mind that these callbacks do not have to act as end points; loadUser can perform a task, then call next to continue matching subsequent routes. Thus, the actual methods are router. You can provide multiple callbacks, and all are treated equally, and behave just like middleware, except that these callbacks may invoke next 'route' to bypass the remaining route callback s.
You can use this mechanism to perform pre-conditions on a route then pass control to subsequent routes when there is no reason to proceed with the route matched. The following snippet illustrates the most simple route definition possible.
Express translates the path strings to regular expressions, used internally to match incoming requests. Adds callback triggers to route parameters, where name is the name of the parameter and callback is the callback function. Although name is technically optional, using this method without it is deprecated starting with Express v4. Hence, param callbacks defined on router will be triggered only by route parameters defined on router routes. A param callback will be called only once in a request-response cycle, even if the parameter is matched in multiple routes, as shown in the following examples.
The following section describes router. The behavior of the router. This function is a custom implementation of how router. In this example, the router. Instead of accepting a name and a callback, router. Returns an instance of a single route which you can then use to handle HTTP verbs with optional middleware.
Building on the router. When you use router. For this purpose, you can consider method handlers to belong to the route to which they were added. This method is similar to app. A simple example and use case is described below. Middleware is like a plumbing pipe: The order in which you define middleware with router.
They are invoked sequentially, thus the order defines middleware precedence. For example, usually a logger is the very first middleware you would use, so that every request gets logged. Now suppose you wanted to ignore logging requests for static files, but to continue logging routes and middleware defined after logger. You would simply move the call to express. Although these middleware functions are added via a particular router, when they run is defined by the path they are attached to not the router.
Therefore, middleware added via one router may run for other routers if its routes match. For example, this code shows two different routers mounted on the same path:.