Skip to content

Latest commit

 

History

History
231 lines (140 loc) · 7.39 KB

README.md

File metadata and controls

231 lines (140 loc) · 7.39 KB
Raw
About stdlib...

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

startsWith

NPM version Build Status Coverage Status

Test if a string starts with the characters of another string.

Usage

import startsWith from 'https://cdn.jsdelivr.net/gh/stdlib-js/string-base-starts-with@esm/index.mjs';

startsWith( str, search, position )

Tests if a string starts with the characters of another string.

var str = 'To be, or not to be, that is the question.';

var bool = startsWith( str, 'To be', 0 );
// returns true

bool = startsWith( str, 'to be', 0 );
// returns false

To search from a specific character index, provide a position value (zero-based). If provided a negative position, the start index is determined relative to the string end (i.e., pos = str.length + position).

var str = 'Remember the story I used to tell you when you were a boy?';

var bool = startsWith( str, 'the story', 0 );
// returns false

bool = startsWith( str, 'the story', 9 );
// returns true

bool = startsWith( str, 'you', -15 );
// returns true

If provided an empty search string, the function always returns true.

var str = 'beep boop';

var bool = startsWith( str, '', 0 );
// returns true

Notes

  • This function differs from String.prototype.startsWith in the following ways:

    • The function assumes string values for the first and second arguments and assumes that the position argument is an integer value.
    • The function does not clamp negative position values. Instead, when provided a negative position, the function resolves the starting search position relative to the end of the string.
    • Except when provided an empty search string, the function always returns false if a position resolves to a starting search position which exceeds the bounds of the input string.

Examples

<!DOCTYPE html>
<html lang="en">
<body>
<script type="module">

import startsWith from 'https://cdn.jsdelivr.net/gh/stdlib-js/string-base-starts-with@esm/index.mjs';

var str = 'Fair is foul, and foul is fair, hover through fog and filthy air';

var bool = startsWith( str, 'Fair', 0 );
// returns true

bool = startsWith( str, 'fair', 0 );
// returns false

bool = startsWith( str, 'foul', 8 );
// returns true

bool = startsWith( str, 'filthy', -10 );
// returns true

</script>
</body>
</html>

Notice

This package is part of stdlib, a standard library with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

Chat

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.