Swift's String.hasPrefix in TypeScript

How to use

Install via yarn add locutus and import: import { hasPrefix } from 'locutus/swift/String/hasPrefix'.

Or with CommonJS: const { hasPrefix } = require('locutus/swift/String/hasPrefix')

Use a bundler that supports tree-shaking so you only ship the functions you actually use. Vite, webpack, Rollup, and Parcel all handle this. For server-side use this is less of a concern.

Examples

These examples are extracted from test cases that automatically verify our functions against their native counterparts.

#	code	expected result
1	hasPrefix('Locutus', 'Loc')	true
2	hasPrefix('Locutus', 'loc')	false
3	hasPrefix('', '')	true

Notes

• Returns true when str begins with prefix, like Swift hasPrefix(_:).

Here's what our current TypeScript equivalent to Swift's String.hasPrefix looks like.

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

Copy code

export function hasPrefix(str: string, prefix: string): boolean {
  //  discuss at: https://locutus.io/swift/String/hasPrefix/
  // original by: Kevin van Zonneveld (https://kvz.io)
  //      note 1: Returns true when str begins with prefix, like Swift hasPrefix(_:).
  //   example 1: hasPrefix('Locutus', 'Loc')
  //   returns 1: true
  //   example 2: hasPrefix('Locutus', 'loc')
  //   returns 2: false
  //   example 3: hasPrefix('', '')
  //   returns 3: true

  return String(str).startsWith(String(prefix))
}

export function hasPrefix(str, prefix) {
  //  discuss at: https://locutus.io/swift/String/hasPrefix/
  // original by: Kevin van Zonneveld (https://kvz.io)
  //      note 1: Returns true when str begins with prefix, like Swift hasPrefix(_:).
  //   example 1: hasPrefix('Locutus', 'Loc')
  //   returns 1: true
  //   example 2: hasPrefix('Locutus', 'loc')
  //   returns 2: false
  //   example 3: hasPrefix('', '')
  //   returns 3: true

  return String(str).startsWith(String(prefix))
}

Improve this function

Locutus is a community effort following The McDonald's Theory: we ship first iterations, hoping others will improve them. If you see something that could be better, we'd love your contribution.

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We will then review it. If it's useful to the project and in line with our contributing guidelines your work will become part of Locutus and you'll be automatically credited in the authors section accordingly.

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