Common API Reference

Context Object

The context object provides information about the current function execution and allows you to interact with the Azure Functions runtime.

Properties

Name	Type	Description
invocationId	string	The unique identifier for the current function invocation.
bindingData	object	An object containing metadata related to the trigger and bindings. The exact properties vary depending on the trigger.
log	Logger Object	An object used for writing logs during function execution.
res	object	For HTTP triggered functions, this is the response object used to send a response back to the client.
done()	function	A callback function that must be called to signal that the function execution is complete. It can optionally accept an error object or a result object.

Methods

context.done(err, result)

Signals the completion of the function execution.

• err (optional): An error object if the function execution failed.
• result (optional): The result of the function execution.

Logger Object

The log object (accessed via context.log) provides methods for writing diagnostic information during function execution.

Methods

• log.verbose(message: string): Logs a verbose message.
• log.debug(message: string): Logs a debug message.
• log.info(message: string): Logs an informational message.
• log.warn(message: string): Logs a warning message.
• log.error(message: string): Logs an error message.

These methods can take multiple arguments, which will be formatted according to standard string interpolation rules.

context.log.info('Processing request for user ID: {userId}', { userId: 123 });

HTTP Trigger Specifics

When a function is triggered by an HTTP request, the context object gains additional properties related to HTTP.

context.req (Request Object)

Represents the incoming HTTP request.

Name	Type	Description
method	string	The HTTP method (e.g., 'GET', 'POST').
url	string	The request URL.
headers	object	An object containing request headers.
query	object	An object containing URL query parameters.
params	object	An object containing route parameters.
body	any	The request body, parsed according to the Content-Type header.

context.res (Response Object)

Represents the outgoing HTTP response. You set properties on this object to define the response.

Name	Type	Description
status	number	The HTTP status code (e.g., 200, 404). Defaults to 200.
body	any	The response body.
headers	object	An object containing response headers.

Example of returning an HTTP response:

module.exports = async function (context, req) {
    context.log('JavaScript HTTP trigger function processed a request.');
    const name = (req.query.name || (req.body && req.body.name));
    const responseMessage = name
        ? 'Hello, ' + name + '!'
        : "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response.";

    context.res = {
        status: 200,
        body: responseMessage
    };

    context.done();
};