findLastIndex

Returns the index of the last element in an array that satisfies a predicate function

Usage

import { findLastIndex } from '@accelint/core';

// Find index of last even number
const lastEvenIndex = findLastIndex((x: number) => x % 2 === 0)([1, 2, 3, 4, 5]);
// 3

// Partial application
const findLastNegative = findLastIndex((x: number) => x < 0);
findLastNegative([5, -3, 10, -8]); // 3

Reference

function findLastIndex<T>(
  predicate: (element: T, index: number) => boolean
): (arr: T[]) => number

Parameters

Parameter	Type	Description
`predicate`	`(element: T, index: number) => boolean`	Function called for each element from the end until it returns `true`. Receives the element and its index.

Returns

Returns a curried function that accepts an array and returns the index of the last matching element, or -1 if no match is found.

Type Parameters

T - The type of elements in the array

Examples

Example: Finding last occurrence

import { findLastIndex } from '@accelint/core';

const data = [1, 2, 3, 2, 1];
const lastTwoIndex = findLastIndex((x: number) => x === 2)(data);
// 3 (finds the second occurrence of 2)

Example: Finding by complex condition

import { findLastIndex } from '@accelint/core';

interface Task {
  id: number;
  completed: boolean;
  priority: 'low' | 'medium' | 'high';
}

const tasks: Task[] = [
  { id: 1, completed: true, priority: 'high' },
  { id: 2, completed: false, priority: 'medium' },
  { id: 3, completed: true, priority: 'low' }
];

const lastCompletedIndex = findLastIndex((t: Task) => t.completed)(tasks);
// 2

Example: Using index parameter

import { findLastIndex } from '@accelint/core';

// Find last element where value equals index
const data = [0, 2, 2, 3, 5];
const index = findLastIndex((value: number, idx: number) => value === idx)(data);
// 3 (value 3 at index 3)

Good to know: The search starts from the end of the array and moves backward. The predicate is called only until a matching element is found, then iteration stops immediately.

findIndex - Find index from the start of array
findLast - Find the last matching element
find - Find the first matching element

findLastIndex

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