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43 lines
1.5 KiB
43 lines
1.5 KiB
'use strict'; |
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var $TypeError = require('es-errors/type'); |
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var callBound = require('call-bound'); |
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var isInteger = require('math-intrinsics/isInteger'); |
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var $strSlice = callBound('String.prototype.slice'); |
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// https://262.ecma-international.org/15.0/#sec-stringpad |
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module.exports = function StringPad(S, maxLength, fillString, placement) { |
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if (typeof S !== 'string') { |
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throw new $TypeError('Assertion failed: `S` must be a String'); |
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} |
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if (!isInteger(maxLength) || maxLength < 0) { |
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throw new $TypeError('Assertion failed: `maxLength` must be a non-negative integer'); |
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} |
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if (typeof fillString !== 'string') { |
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throw new $TypeError('Assertion failed: `fillString` must be a String'); |
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} |
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if (placement !== 'start' && placement !== 'end' && 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 stringLength = S.length; // step 1 |
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if (maxLength <= stringLength) { return S; } // step 2 |
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if (fillString === '') { return S; } // step 3 |
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var fillLen = maxLength - stringLength; // step 4 |
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// 5. Let _truncatedStringFiller_ be the String value consisting of repeated concatenations of _fillString_ truncated to length _fillLen_. |
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var truncatedStringFiller = ''; |
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while (truncatedStringFiller.length < fillLen) { |
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truncatedStringFiller += fillString; |
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} |
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truncatedStringFiller = $strSlice(truncatedStringFiller, 0, fillLen); |
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if (placement === 'start' || placement === 'START') { return truncatedStringFiller + S; } // step 6 |
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return S + truncatedStringFiller; // step 7 |
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};
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