Left pad a string.
npm install @stdlib/string-left-padAlternatively,
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var lpad = require( '@stdlib/string-left-pad' );Left pads a string such that the padded string has a length of at least len.
var str = lpad( 'a', 5 );
// returns ' a'By default, an input string is padded with a Unicode "space" character (U+0020). To pad with a different character or sequence of characters, provide a pad string.
var str = lpad( 'beep', 10, 'b' );
// returns 'bbbbbbbeep'
str = lpad( 'boop', 12, 'beep' );
// returns 'beepbeepboop'-
An output string is not guaranteed to have a length of exactly
len, but to have a length of at leastlen. To generate a padded string having a length equal tolenvar str = lpad( 'boop', 10, 'beep' ); // => length 12 // returns 'beepbeepboop' str = str.substring( str.length-10 ); // => length 10 // returns 'epbeepboop'
-
This function differs from
String.prototype.padStartin the following ways:- The function is not guaranteed to return a string having a length exactly equal to
len(as explained above). - The function does not truncate
pad(from the end) in order to ensure the returned string has lengthlen.
To replicate
String.prototype.padStarttruncation behaviorvar floorb = require( '@stdlib/math-base-special-floorb' ); function padStart( str, len, pad ) { var n; if ( len <= str.length ) { return str; } n = floorb( len-str.length, 1, pad.length ) + str.length; return pad.substring( 0, len-n ) + lpad( str, n, pad ); } var str = padStart( 'boop', 10, 'beep' ); // returns 'bebeepboop'
- The function is not guaranteed to return a string having a length exactly equal to
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var lpad = require( '@stdlib/string-left-pad' );
var str = 'beep';
var i;
for ( i = 0; i < 100; i++ ) {
console.log( lpad( str, discreteUniform( str.length, str.length+10 ), 'b' ) );
}To use the module as a general utility, install the module globally
npm install -g @stdlib/string-left-padUsage: lpad [options] --len=<length> [<string>]
Options:
-h, --help Print this message.
-V, --version Print the package version.
--len length Minimum string length.
--pad str String used to pad. Default: ' '.
--split sep Delimiter for stdin data. Default: '/\\r?\\n/'.
-
If the split separator is a regular expression, ensure that the
splitoption is either properly escaped or enclosed in quotes.# Not escaped... $ echo -n $'beep\nboop' | lpad -len 8 --split /\r?\n/ # Escaped... $ echo -n $'beep\nboop' | lpad -len 8 --split /\\r?\\n/
-
The implementation ignores trailing delimiters.
$ lpad beep --len 10 --pad b
bbbbbbbeepTo use as a standard stream,
$ echo -n 'beep' | lpad --len 8
beepBy default, when used as a standard stream, the implementation assumes newline-delimited data. To specify an alternative delimiter, set the split option.
$ echo -n 'boop\tbeep' | lpad --len 8 --split '\t'
boop
beep@stdlib/string/pad: pad a string.@stdlib/string/right-pad: right pad a string.
This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
See LICENSE.
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