211 lines
5.0 KiB
Markdown
211 lines
5.0 KiB
Markdown
<!--
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@license Apache-2.0
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Copyright (c) 2020 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# codePointAt
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> Return a Unicode [code point][code-point] from a string at a specified position.
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- Package usage documentation. -->
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<section class="usage">
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## Usage
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```javascript
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var codePointAt = require( '@stdlib/string/code-point-at' );
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```
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#### codePointAt( string, position\[, backward] )
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Returns a Unicode [code point][code-point] from a string at a specified position.
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```javascript
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var out = codePointAt( 'last man standing', 4 );
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// returns 32
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```
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The function supports providing a `boolean` argument for performing backward iteration for low surrogates.
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```javascript
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var out = codePointAt( '🌷', 1, true );
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// returns 127799
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```
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</section>
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<!-- /.usage -->
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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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## Notes
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This function differs from [`String.prototype.codePointAt`][mdn-string-codepointat] in the following ways:
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- The function supports providing a `boolean` argument for performing backward iteration for low surrogates. [`String.prototype.codePointAt`][mdn-string-codepointat] simply returns the low surrogate value if no [UTF-16][utf-16] surrogate pair begins at the specified position. If invoked with `backward` set to `true`, this function will return the code point after aggregating with the preceding high surrogate, if the specified position does not mark the start of a surrogate pair.
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</section>
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<!-- /.notes -->
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<!-- Package usage examples. -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var codePointAt = require( '@stdlib/string/code-point-at' );
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console.log( codePointAt( 'last man standing', 4 ) );
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// => 32
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console.log( codePointAt( 'presidential election', 8, true ) );
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// => 116
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console.log( codePointAt( 'अनुच्छेद', 2 ) );
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// => 2369
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console.log( codePointAt( '🌷', 1, true ) );
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// => 127799
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```
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</section>
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<!-- /.examples -->
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<!-- Section for describing a command-line interface. -->
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* * *
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<section class="cli">
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## CLI
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<!-- CLI usage documentation. -->
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<section class="usage">
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### Usage
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```text
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Usage: code-point-at [options] [<string>] --pos=<index>
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Options:
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-h, --help Print this message.
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-V, --version Print the package version.
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-b, --backward Backward iteration for low surrogates.
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--pos index Position in string.
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```
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</section>
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<!-- /.usage -->
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<!-- CLI usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<!-- CLI usage examples. -->
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<section class="examples">
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### Examples
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```bash
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$ code-point-at --pos=2 अनुच्छेद
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2369
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```
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To use as a [standard stream][standard-streams],
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```bash
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$ echo -n 'अनुच्छेद' | code-point-at --pos=2
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2369
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```
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</section>
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<!-- /.examples -->
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</section>
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<!-- /.cli -->
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<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="references">
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</section>
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<!-- /.references -->
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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
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<section class="related">
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* * *
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## See Also
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- <span class="package-name">[`@stdlib/string/from-code-point`][@stdlib/string/from-code-point]</span><span class="delimiter">: </span><span class="description">create a string from a sequence of Unicode code points.</span>
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</section>
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<!-- /.related -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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[code-point]: https://en.wikipedia.org/wiki/Code_point
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[standard-streams]: https://en.wikipedia.org/wiki/Standard_streams
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[mdn-string-codepointat]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/codePointAt
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[utf-16]: https://en.wikipedia.org/wiki/UTF-16
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<!-- <related-links> -->
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[@stdlib/string/from-code-point]: https://github.com/stdlib-js/string/tree/main/from-code-point
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<!-- </related-links> -->
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</section>
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<!-- /.links -->
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