In this article, we will go over the most commonly used so you can learn different approaches and understand how they work. There are numerous methods for looping through an array in JavaScript. Here's an interactive scrim about how to loop through an array in JavaScript: What are Loops in JavaScript?Ī loop is a type of computer program that allows us to repeat a specific operation a predetermined number of times without having to write that operation individually.įor example, if we have an array and want to output each element in the array, rather than using the index number to do so one by one, we can simply loop through and perform this operation once. Knowing that these single variables contain a list of elements, you might want to create a list of these elements so that you can perform individual functions with them and much more. It is an ordered list of values, and each value is referred to as an element, which is specified by an index. The key difference between the two is that foreach automatically starts at the front of the array, whereas list()/ each() does not.An array is a single variable used to store elements of different datatypes so that they can be accessed through a single variable. In practice, however, you will find foreach loops and list()/ each() loops in about equal proportions, despite the latter option being slower. Generally speaking, using foreach loops is the most optimised way to loop through an array, and is also the easiest to read. There is a lot more detail on array cursors later. The meaning of that first line is "get the current element in the array, and assign its key to $var and its value to $val, then advance the array cursor. To start with, each() will return the first element, then the second element, then the third, and so on, until it finds there are no elements left, in which case it will return false and end the loop. All arrays have a cursor, and you can freely move it around - it is used in the while loop above, where we need to iterate through an array. "Array cursor" is the technical term for the element of an array that is currently being read. Each() takes an array as its parameter, and returns the current key and value in that array before advancing the array cursor. List() is a function that does the opposite of array() - it takes an array, and converts it into individual variables. The second way to use foreach does allow you to extract keys, and looks like this:Īnother commonly used way to loop over arrays is using the list() and each() functions, like this: In this situation, the array keys are ignored completely, which usually makes most sense when they have been auto-generated (i.e. Here the array $array is looped through and its values are extracted into $val. The easiest way to use foreach looks like this: However, there is a quick and easy way to accomplish the same thing: a foreach loop, which itself has two versions. As a result, code like this should generally be avoided: That is, it can have its keys out of order or entirely missing. For example, an array may have keys 0, 1, 2, 5, 3, 6, 7. However, these numbers cannot be guaranteed to exist within the array in any given order, or even to exist at all - they are just key values themselves. If you do not specify a key, as in the first example, PHP will just assign incrementing numbers starting with 0.
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