locutus
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Locutus other languages' standard libraries to JavaScript for fun and educational purposes
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JavaScript
import { _phpCastString as _php_cast_string } from "../_helpers/_phpCastString.js";
import { ini_get } from "../info/ini_get.js";
export function substr(input, start, len) {
// discuss at: https://locutus.io/php/substr/
// original by: Martijn Wieringa
// bugfixed by: T.Wild
// improved by: Onno Marsman (https://twitter.com/onnomarsman)
// improved by: Brett Zamir (https://brett-zamir.me)
// revised by: Theriault (https://github.com/Theriault)
// revised by: Rafał Kukawski
// note 1: Handles rare Unicode characters if 'unicode.semantics' ini (PHP6) is set to 'on'
// example 1: substr('abcdef', 0, -1)
// returns 1: 'abcde'
// example 2: substr(2, 0, -6)
// returns 2: false
// example 3: ini_set('unicode.semantics', 'on')
// example 3: substr('a\uD801\uDC00', 0, -1)
// returns 3: 'a'
// example 4: ini_set('unicode.semantics', 'on')
// example 4: substr('a\uD801\uDC00', 0, 2)
// returns 4: 'a\uD801\uDC00'
// example 5: ini_set('unicode.semantics', 'on')
// example 5: substr('a\uD801\uDC00', -1, 1)
// returns 5: '\uD801\uDC00'
// example 6: ini_set('unicode.semantics', 'on')
// example 6: substr('a\uD801\uDC00z\uD801\uDC00', -3, 2)
// returns 6: '\uD801\uDC00z'
// example 7: ini_set('unicode.semantics', 'on')
// example 7: substr('a\uD801\uDC00z\uD801\uDC00', -3, -1)
// returns 7: '\uD801\uDC00z'
const str = _php_cast_string(input);
const multibyte = ini_get('unicode.semantics') === 'on';
const chars = multibyte ? str.match(/[\uD800-\uDBFF][\uDC00-\uDFFF]|[\s\S]/g) || [] : null;
const inputLength = chars ? chars.length : str.length;
let end = inputLength;
if (start < 0) {
start += end;
}
if (typeof len !== 'undefined') {
if (len < 0) {
end = len + end;
}
else {
end = len + start;
}
}
if (start > inputLength || start < 0 || start > end) {
return false;
}
if (chars) {
return chars.slice(start, end).join('');
}
return str.slice(start, end);
}