92 lines
2.7 KiB
JavaScript
92 lines
2.7 KiB
JavaScript
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive;
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var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
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var repeat = require( './../../repeat' );
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var ceil = require( '@stdlib/math/base/special/ceil' );
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var format = require( './../../format' );
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var FLOAT64_MAX_SAFE_INTEGER = require( '@stdlib/constants/float64/max-safe-integer' );
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// MAIN //
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/**
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* Left pads a string such that the padded string has a length of at least `len`.
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*
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* @param {string} str - string to pad
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* @param {NonNegativeInteger} len - minimum string length
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* @param {string} [pad=' '] - string used to pad
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* @throws {TypeError} first argument must be a string
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* @throws {TypeError} second argument must be a nonnegative integer
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* @throws {TypeError} third argument must be a string
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* @throws {RangeError} padding must have a length greater than `0`
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* @returns {string} padded string
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*
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* @example
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* var str = lpad( 'a', 5 );
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* // returns ' a'
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*
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* @example
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* var str = lpad( 'beep', 10, 'b' );
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* // returns 'bbbbbbbeep'
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*
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* @example
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* var str = lpad( 'boop', 12, 'beep' );
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* // returns 'beepbeepboop'
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*/
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function lpad( str, len, pad ) {
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var n;
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var p;
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if ( !isString( str ) ) {
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throw new TypeError( format( 'invalid argument. First argument must be a string. Value: `%s`.', str ) );
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}
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if ( !isNonNegativeInteger( len ) ) {
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throw new TypeError( format( 'invalid argument. Second argument must be a nonnegative integer. Value: `%s`.', len ) );
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}
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if ( arguments.length > 2 ) {
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p = pad;
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if ( !isString( p ) ) {
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throw new TypeError( format( 'invalid argument. Third argument must be a string. Value: `%s`.', p ) );
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}
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if ( p.length === 0 ) {
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throw new RangeError( 'invalid argument. Third argument must not be an empty string.' );
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}
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} else {
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p = ' ';
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}
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if ( len > FLOAT64_MAX_SAFE_INTEGER ) {
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throw new RangeError( format( 'invalid argument. Output string length exceeds maximum allowed string length. Value: `%u`.', len ) );
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}
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n = ( len - str.length ) / p.length;
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if ( n <= 0 ) {
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return str;
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}
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n = ceil( n );
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return repeat( p, n ) + str;
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}
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// EXPORTS //
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module.exports = lpad;
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