44 lines
1.2 KiB
JavaScript
44 lines
1.2 KiB
JavaScript
'use strict';
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var GetIntrinsic = require('../GetIntrinsic');
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var $TypeError = GetIntrinsic('%TypeError%');
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var callBound = require('../helpers/callBound');
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var ToLength = require('./ToLength');
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var ToString = require('./ToString');
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var $strSlice = callBound('String.prototype.slice');
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// https://tc39.es/ecma262/2020/#sec-stringpad
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module.exports = function StringPad(O, maxLength, fillString, placement) {
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if (placement !== 'start' && placement !== 'end') {
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throw new $TypeError('Assertion failed: `placement` must be "start" or "end"');
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}
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var S = ToString(O);
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var intMaxLength = ToLength(maxLength);
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var stringLength = S.length;
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if (intMaxLength <= stringLength) {
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return S;
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}
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var filler = typeof fillString === 'undefined' ? ' ' : ToString(fillString);
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if (filler === '') {
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return S;
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}
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var fillLen = intMaxLength - stringLength;
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// the String value consisting of repeated concatenations of filler truncated to length fillLen.
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var truncatedStringFiller = '';
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while (truncatedStringFiller.length < fillLen) {
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truncatedStringFiller += filler;
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}
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truncatedStringFiller = $strSlice(truncatedStringFiller, 0, fillLen);
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if (placement === 'start') {
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return truncatedStringFiller + S;
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}
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return S + truncatedStringFiller;
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};
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