The slowest AJAX request would always win the user’s attention by blindly replacing results, even when those replaced results may have been newer. Why did that happen? Because each AJAX success handler was given access to directly update the suggestion list that was displayed to users. It would trigger race conditions, where newer suggestions would be replaced by outdated suggestions. The only problem was that users often type faster than an API autocomplete search response can be returned, which caused some strange bugs. AJAX-powered autocomplete was suddenly all the rage. This was around the time Google Instant landed, which displays instant search results as you type your search query. Several years ago I was working on an app that allowed users to search a database for musical artists and load the artist’s music playlist into a web player. Pure functions are also extremely independent - easy to move around, refactor, and reorganize in your code, making your programs more flexible and adaptable to future changes. Their independent nature also makes them great candidates for parallel processing across many CPUs, and across entire distributed computing clusters, which makes them essential for many types of scientific and resource-intensive computing tasks. Pure functions are completely independent of outside state, and as such, they are immune to entire classes of bugs that have to do with shared mutable state. Pure functions have many beneficial properties, and form the foundation of functional programming. Pure functions are stupid simple in the best possible way. Perhaps the most important design principle in computer science is KISS (Keep It Simple, Stupid). They are the simplest reusable building blocks of code in a program. Pure functions take some input and return some output based on that input. Meaning, if it is practical to implement a program requirement using pure functions, you should use them over other options. I recommend that you favor pure functions. If you want referential transparency, you need to use pure functions.Ī dead giveaway that a function is impure is if it makes sense to call it without using its return value. This is true because `double()` is a pure function, but if `double()` had side-effects, such as saving the value to disk or logging to the console, you couldn’t simply replace `double(5)` with 10 without changing the meaning. So, `console.log( double(5) ) ` is the same as `console.log(10) ` Given the same input, will always return the same output.Remember when I said that in math functions, you could replace `f(2)` with `4`? In this case, the JavaScript engine replaces `double(5)` with the answer, `10`. You can examine the function’s output using `console.log()`: console.log( double(5) ) // 10 Now let’s convert that function to JavaScript: const double = x => x * 2 So any place you see f(2) you can substitute 4. In algebra, this means exactly the same thing as writing: To use this function, we simply provide a value for x: Which means that we’re declaring a function called f and it takes an argument called x and multiplies x by 2. You’ve probably seen functions in algebra. Math has functions, too, and they work a lot like functions in JavaScript. Good programmers give functions descriptive names so that when we see the code, we can see the function names and understand what the function does. They help us process data in useful ways. In this case, the largest number we passed in was 8, and that’s the number that got returned.įunctions are really important in computing and math. `Math.max()` is a function that takes any number of arguments and returns the largest argument value. In this example, 2, 8, & 5 are arguments. `Math.max()` takes numbers as arguments and returns the largest number: Math.max(2, 8, 5) // 8 A function will take the inputs and return the corresponding output. Functions map input arguments to return values, meaning that for each set of inputs, there exists an output. I/O: Some functions exist to communicate with other parts of the system, such as the screen, storage, system logs, or network. ![]() The sequence is known as a procedure, and programming in this style is known as procedural programming.
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