Array.prototype.indexOf()
Array.prototype.indexOf() is a JavaScript method in the Array category. Returns the first index at which a given element can be found. The syntax is array.indexOf(searchElement, fromIndex). It returns the index, or -1 if not found. A typical example: [1, 2, 3].indexOf(2) // 1. Its time complexity is O(n), which matters when it runs over large inputs. The TypeScript signature is (searchElement: T, fromIndex?: number): number. A close sibling is Array.prototype.map(), which creates a new array populated with the results of calling a provided function on every element. A close sibling is Array.prototype.filter(), which creates a new array with all elements that pass the test implemented by the provided function. A close sibling is Array.prototype.reduce(), which executes a reducer function on each element, resulting in a single output value. A close sibling is Array.prototype.forEach(), which executes a provided function once for each array element. More about this category: Array methods for manipulating arrays — map, filter, reduce, find, and more.