From the course: Learning Functional Programming with JavaScript (ES5)
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Callbacks with arguments - JavaScript Tutorial
From the course: Learning Functional Programming with JavaScript (ES5)
Callbacks with arguments
- [Narrator] With our simple setTimeout example, the function we passed was a function with no arguments. This is actually very rarely the case. Most asynchronous functions that we perform pass the results of the operation to our function as an argument. For example, it might pass the results that we obtain when reading from a database or reading a file. In Node.js especially, the standard form is to pass the result of the asynchronous function as the second argument, and any errors the function encounters as the first argument. As an example, let's take a look at how we read a file asynchronously in Node.js. Fs is a standard library included with Node.js that allows us to work with the file system. Note that we don't have to use npm to install it. Now, when we read a file using fs.readFile, the results of opening the file are passed to our function. The first argument will contain any errors that occurred during the operation such as if the file didn't exist, and the second one will…
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