Press n or j to go to the next uncovered block, b, p or k for the previous block.
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* @license Apache-2.0
*
* Copyright (c) 2023 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
var isInteger = require( '@stdlib/assert/is-integer' ).isPrimitive;
var format = require( '@stdlib/string/format' );
// VARIABLES //
var RE_UTF16_LOW_SURROGATE = /[\uDC00-\uDFFF]/; // TODO: replace with stdlib pkg
var RE_UTF16_HIGH_SURROGATE = /[\uD800-\uDBFF]/; // TODO: replace with stdlib pkg
// MAIN //
/**
* Returns the position of the next Unicode code point in a string after a specified position.
*
* @param {string} str - input string
* @param {integer} [fromIndex=0] - position
* @throws {TypeError} first argument must be a string
* @throws {TypeError} second argument must be an integer
* @returns {integer} position of the next Unicode code point
*
* @example
* var out = nextCodePointIndex( 'last man standing', 4 );
* // returns 5
*
* @example
* var out = nextCodePointIndex( 'presidential election', 8 );
* // returns 9
*
* @example
* var out = nextCodePointIndex( '𐒻𐓟𐒻𐓟', 0 );
* // returns 2
*
* @example
* var out = nextCodePointIndex( '🌷' );
* // returns -1
*/
function nextCodePointIndex( str, fromIndex ) {
var lastIndex;
var len;
var idx;
var i;
var j;
if ( !isString( str ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a string. Value: `%s`.', str ) );
}
if ( arguments.length > 1 ) {
if ( !isInteger( fromIndex ) ) {
throw new TypeError( format( 'invalid argument. Second argument must be an integer. Value: `%s`.', fromIndex ) );
}
idx = fromIndex;
} else {
idx = 0;
}
len = str.length;
if ( idx < 0 ) {
idx += len;
if ( idx < 0 ) {
idx = 0;
}
}
lastIndex = len - 1;
if ( idx >= lastIndex ) {
return -1;
}
// Check for a high UTF-16 surrogate...
i = idx + 1;
j = i + 1;
if ( RE_UTF16_HIGH_SURROGATE.test( str[ idx ] ) ) {
// Check whether the high surrogate is paired with a low surrogate...
if ( RE_UTF16_LOW_SURROGATE.test( str[ i ] ) ) {
// We found a surrogate pair:
return ( j >= lastIndex ) ? -1 : j;
}
return i;
}
return i;
}
// EXPORTS //
module.exports = nextCodePointIndex;
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