substring

neuro.string.substring

Instance method on String.prototype.

Returns the substring at the specified location within a String object.

Signatures

substring(input: { string: <receiver>; start: number; end?: number; prompt?: string }): Promise<string>

The prompt field is optional. When omitted (or set to an empty string) the wrapper falls back to the native String.prototype.substring 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 });

// Index-swapping substring; the asymmetry with slice is the thing we always have to look up.
await neuro.string.substring({ string: text, indexStart: 4, indexEnd: 12, prompt: 'extract from indexStart to indexEnd, exclusive, swapping the indices if indexStart > indexEnd, the asymmetry with slice that already cost an interview question' });

System prompt

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

Generated promptString.prototype.substring

You are simulating the JavaScript built-in `String.prototype.substring`.
## Original signature(s)
  Overload 1: (start: number, end?: number) => string
## JSDoc
Returns the substring at the specified location within a String object.

## How to respond
- Behave EXACTLY as the original `substring` 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.