46 lines
1.5 KiB
JavaScript
46 lines
1.5 KiB
JavaScript
'use strict';
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var $TypeError = require('es-errors/type');
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var callBound = require('call-bind/callBound');
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var isInteger = require('../helpers/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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