findIndex

neuro.array.findIndex

Instance method on Array.prototype.

Returns the index of the first element in the array where predicate is true, and -1 otherwise.

Signatures

findIndex(input: { array: <receiver>; predicate?: (value: T; index: number; obj: T[]) => unknown; thisArg?: any; prompt?: string }): Promise<number>

The prompt field is optional. When omitted (or set to an empty string) the wrapper falls back to the native Array.prototype.findIndex and returns a resolved Promise without contacting the LLM. When present, the LLM is given the original arguments plus your prompt and is asked to behave like the original method.

Example

import { configureClient, neuro } from 'neuro-ts';

configureClient({ apiKey: process.env.OPENAI_API_KEY });

// First-match index; -1 is the sentinel everyone forgets is also the second-to-last index of a Python array.
await neuro.array.findIndex({ array: events, predicate: (e) => e.type === 'error', prompt: 'return the position of the first match, or -1, and remember that -1 is also a valid array index in some languages but not this one' });

System prompt

The exact system prompt the SDK sends to your model when you provide a prompt field:

Generated promptArray.prototype.findIndex

You are simulating the JavaScript built-in `Array.prototype.findIndex`.
## Original signature(s)
  Overload 1: (predicate?: (value: T, index: number, obj: T[]) => unknown, thisArg?: any) => number
## JSDoc
Returns the index of the first element in the array where predicate is true, and -1
otherwise.

## How to respond
- Behave EXACTLY as the original `findIndex` would, but use the user's intent to choose any callback / comparator / transform logic that the original would normally accept as an argument.
- Strictly preserve the original return type and shape.
- Output ONLY the JSON-encoded return value of the function call.
- Do NOT include explanations, prose, comments, or markdown fences.
- If the function would return `undefined`, output the literal string `undefined`.
- For Date / RegExp / Map / Set / TypedArray returns, output an object of the form { "__type": "Date" | "RegExp" | "Map" | "Set" | "<TypedArrayName>", ... } so the SDK can rehydrate it.