![]() "a - b" is negative when b is greater than a, positive when With that, the issue of sorting numbers can be fixed by passing the correct comparison function. 0 if the order of the elements should stay the same.a positive number if the first argument should be sorted after the second.a negative number if the first argument should be sorted before the second.The comparison function itself is called with two arguments which are two elements of the array. To customize the sorting behavior, you can pass a comparison function as an argument. Because the string '10' comes before '2' in dictionary order. This default behavior leads to wrong results when you try to sort numbers. Sort also returns that modified array which is convenient if you want to chain other methods to it. The sorting happens in-place which means the original array is modified. Remove 2 elements, starting at index 3 and insert 2 elementsĬonst removed = arr.splice(3, 2, '4', '5') īy default, sort sorts the elements of an array by first converting them to strings and then applying string comparison (see Concept Comparison). Splice returns the elements that have been removed. the elements to insert in the array (optional).the index of the element where to start modifying the array.Removes or replaces and/or adds new elements of an array. You can also use negative numbers, that represent the indexes The start index defaults to 0, and the end index defaults to the array length. The element at the end index will not be included. Given a start and an end index, creates a sub-array from the array it is called on. This method modifies the array it is called on. Classify the numbers by whether they are odd or not let arr = Īrr.reduce((accumulator, currentValue) => accumulator + currentValue, 0) ![]() This function instructs how the current element must be merged into the accumulator and returns the accumulator that will be used on the next iteration. Reduces the array to a single value using a function that takes an accumulator and the current element of the array as parameters. ![]() ![]() filter (pure)Ĭreates an array by filtering the current one, given a filtering function (that returns true if the element should be kept and false if it should be removed). It is worth noting that the resulting array will always be of the same length as the original. let arr = Ĭonst newArr = arr.map((value) => value - 1) These callback functions are often written as arrow functions. map (pure)Ĭreate a new array by transforming each element according to a function passed as an argument. Some of the most commonly used methods to transform arrays are presented below.Ī full list of available methods can be found in the MDN documentation. Other methods however manipulate the array they are called on and do not return the modified array. Some methods are pure, meaning that they do not modify the original array. These methods make it much easier to convert one array into another than it otherwise would be using a simple for loop or more direct manipulation. In JavaScript, the Array class has many powerful built-in methods for transforming arrays. ![]()
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