findIndex

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

Usage

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

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

// Partial application
const findNegative = findIndex((x: number) => x < 0);
findNegative([5, 10, -3, 8]); // 2

Reference

function findIndex<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 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 first matching element, or -1 if no match is found.

Type Parameters

T - The type of elements in the array

Examples

Example: Finding by property value

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

interface Product {
  id: number;
  name: string;
  inStock: boolean;
}

const products: Product[] = [
  { id: 1, name: 'Laptop', inStock: false },
  { id: 2, name: 'Mouse', inStock: true },
  { id: 3, name: 'Keyboard', inStock: true }
];

const firstInStockIndex = findIndex((p: Product) => p.inStock)(products);
// 1

Example: Using index parameter

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

// Find first element greater than its index
const data = [0, 0, 5, 2, 10];
const index = findIndex((value: number, idx: number) => value > idx)(data);
// 2 (value 5 > index 2)

Example: Element not found

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

const numbers = [1, 3, 5, 7, 9];
const evenIndex = findIndex((x: number) => x % 2 === 0)(numbers);
// -1 (no even numbers found)

Good to know: The predicate is called only until a matching element is found. Once found, iteration stops immediately and the index is returned.

find - Find the first matching element
findLastIndex - Find index from the end of array
indexOf - Find index by value equality
filter - Find all matching elements

findIndex

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