![]() ![]() It has an only input: A separator string to be used. The join method has something in common with the last method we introduced (reduce): It does generate a single output from an array, a string to be more specific, and it can only run on string-based arrays. The reduce method is typically used to synthesize a whole array into one value, like performing a sum for example.ġ0 - String-Array join method The reduce method gets the following inputs:ġ- A function that has the product as the first parameter, and the current element being iterated as a second parameter, a third parameter which is the current element index and the last parameter that provides access to the original array.Ģ- An initial value to be used for the product. This can be hard to grasp at the beginning but the more you look at reduce examples, the easier it becomes to you to understand the syntax. The reduce function keeps track of a new product and the current element, it also receives a parameter for the initial value of the new product. Same as the map function, the filter function takes two arguments:ĩ - The reduce method The filter function is used to evaluate a boolean expression, if true is returned, then the element that is being iterated stays on the new loop, if false is returned then the element is going to be ignored and won't be present on the new array. One of those methods is map.Ĩ - The filter method Oh, and you can use both break and continue keywords for this kind of loop too.ĮS5 added three major methods to iterate an array to generate a new array. This makes you need to handle the scenario of an empty array, since accessing an empty array will result in an error. The do-while loop is really similar to the while loop, but it evaluates the run condition at the end of the execution, resulting in it always running the loop at least one time. If you want to use it to iterate over an array you're going to need to keep track of an index variable too, making it really similar to a C style loop, but with the downside of leaving an index outside of the scope of the loop. The while loop is the fastest one (for some reason), it's syntax is really simple: You can use both break and continue keywords for this kind of loop too. An index modifier that runs at the end of every loop.Its syntax is inherited from the C language and it is composed of three parts: This is one of the most used and taught arrays in Compute Science. The main difference to is the fact that you can use the break keyword to stop the loop and the continue keyword to skip the current iteration. It will avoid object properties and can be used with any object that implements the Symbol too (See advanced usage). It's really similar to the for-in loop, but the main difference between both loops is the fact that for-of is used exclusively on collection types (Maps, Sets, Arrays, TypedArrays, NodeLists, etc.). This is one of the most generous kinds of loops, it's baked in the language specification itself. It also works to loop through arrays, but if you define anything on the array prototype, then it's totally going to be iterated too. It iterates over any custom property defined on an object excluding the default javascript ones. This kind of loop usage is discouraged and reserved only for debugging sometimes, yet you might encounter it out there the wild being used in production. It's the most recommended way to iterate and it's compatible with IE9 The classic forEach array takes two arguments:ġ- A function that contains three parameters: the current item, an index, and the original array.Ģ- A this replacement to be passed to the callback function (It's ignored by arrow functions). In this post, we're going to explore 11 different ways (In no specific order) to iterate an array (Not an object) in Javascript.Īlright, that's a pretty simple array, let's move on.ġ- Trusty old forEach Javascript, our beloved language, Its freedom can be either a blessing or a curse.
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