left-pad / left-pad Goto Github PK

Would it be possible to add an explicit license to this project? Right now it only states BSD in the package.json file, but it doesn't state which variant of the BSD licenses nor who actually holds the copyright on the code.

We are trying to include proper licenses for all our dependencies.

Regards,
Mattias Amnefelt

for kik

str += str is not a constant time operation. What if str is 1GB long?

The first argument of leftPad can be a number and a number can have the value NaN. The following TypeError occurs when NaN is passed as the first argument. I expect to throw an error or give a default value when the first argument cannot be left padded.

file:///path/left-pad/index.js:34
  if (ch === ' ' && len < 10) return cache[len] + str;
                                          ^

TypeError: Cannot read property '1' of undefined
    at leftPad (file:///path/left-pad/index.js:34:43)

i want to see it but npm doesn't work

There is an inconsistency when padding strings containg unicode characters out of BMP plan (ie. code points encoded on two chars in UTF-16).

leftPad('a\u{1f431}b', 4, 'x') => 'a\u{1f431}b' // in: 3 code points, out: 3 code points
leftPad('abc', 4, '\u{1f431}') => '\u{1f431}abc' // in: 3 code points, out: 4 code points

You should maybe specify that left-pad does not handle code points out of BMP plan as single characters.

Failure found using property based testing:
https://runkit.com/dubzzz/5ab9f3d8cc861f0012852eff

One of the falsehoods programmers believe about mono-spaced typefaces is that each character occupies one column, which is terribly wrong. There are both characters that occupy zero columns (like a line-feed or combining accent characters) and characters that occupy two or more columns (like Chinese characters).

left-pad should incorporate code to correctly pad Unicode strings to the specified number of columns, even if the string contains east-asian characters.

When building projects on travis, or when searching for left-pad on npmjs.com, both will report that the package cannot be found.

Here is an excerpt from the travis build log

npm ERR! Linux 3.13.0-40-generic
npm ERR! argv "/home/travis/.nvm/versions/node/v4.2.2/bin/node" "/home/travis/.nvm/versions/node/v4.2.2/bin/npm" "install"
npm ERR! node v4.2.2
npm ERR! npm  v2.14.7
npm ERR! code E404
npm ERR! 404 Registry returned 404 for GET on https://registry.npmjs.org/left-pad
npm ERR! 404 
npm ERR! 404 'left-pad' is not in the npm registry.
npm ERR! 404 You should bug the author to publish it (or use the name yourself!)
npm ERR! 404 It was specified as a dependency of 'line-numbers'
npm ERR! 404 
npm ERR! 404 Note that you can also install from a
npm ERR! 404 tarball, folder, http url, or git url.
npm ERR! Please include the following file with any support request:
npm ERR!     /home/travis/build/coldrye-es/pingo/npm-debug.log
make: *** [deps] Error 1

And here is the standard npmjs.com error page https://www.npmjs.com/package/left-pad

However, if I remove left-pad from my local npm cache and then reinstall it using npm it will happily install [email protected].

Why your code is O(log(n))?
Can you provide a formal proof?

Would you please add a LICENSE file with the text of the license? There are several different variants of the BSD license, and typically the license text should accompany the source code.

The WTFPL and current licensing practices suggest that you should include the text of the license in the package.

The WTFPL FAQ suggest that you should include the full text of the license into the module.

(IANAL, YMMV)

It says in the comments that it is O(log n)

It is not. It must be at least O(n) because each memory location needs to be written to once in order to assign all of them the same value. O(n) is a lower boundary - no algorithm can possibly be faster than that.

In fact, your code is slower than just allocating the memory once and then setting all the characters to the same value. String concatenation takes time, it often cause at least one memory copy.

This code is faster than the concatination-business you are up to:

return pad.repeat(count) + original_string;

I was told to be nice and calm, so I removed the harsh language.

https://dxr.mozilla.org/mozilla-central/source/js/src/builtin/String.js#516-524

@azer As per your post https://medium.com/@azerbike/i-ve-just-liberated-my-modules-9045c06be67c#.tn8s3y7sp I volunteer to take ownership of this module to get it back onto Npm.

@benjamingr asked me to update the benchmarks on pad-left. Here they are.

If you left pad 'foobar' to length of 20.5 the result is a length 20 string as expected, but left pad to length of 10.5 returns 'undefinedfoobar' by failing the cache lookup. Should change behavior so that it returns a length 10 string instead.

A dependency of babel, line-numbers is using left-pad version 0.0.3 as a dependency. Can you please add back in a 0.0.3 version to support the legacy features

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Hello @stevemao

Currently I'm using the version 0.0.3 of this module and there is no clearly specified the license and I cannot find this version on your repository either. The only information available is the one from package.json which seems to be "license: BSD". What license does apply for this version? Is it BSD? What version of BSD would apply?

Thank you!

I can't believe how overly complicated your solution is. This can all be done in 1 line in both ES5 and ES6.

ES6

const leftpad = (str, len, ch = ' ') => Array(Math.max(len - String(str).length + 1, 0)).join(String(ch) ? ch : ' ') + str;

ES5

function leftpad(str, len, ch) { 
  return new Array(Math.max(len - String(str).length + 1, 0)).join(ch != undefined && String(ch) ? ch : ' ') + str; 
}

You've opened eyes on the policies of npm regarding to the people who are "going to be banging on your door and taking down your accounts and stuff like that". To show my gratitude I'd like to ask you to fix an issue with O(n^2) execution time, e.g.

module.exports = function(str, len, ch) {
    return new Array(Math.max(0, len - str.length) + 1).join(ch || ' ') + str;
};

This issue originally came from pad-left's issue #11.

This issue may target left-pad, pad-left, right-pad, and pad-right modules.

ES6 has evolved a lot so far; now it has String.prototype.padStart and String.prototype.repeat.
However, left-pad is still a great module for backward-compatibility.
But since it does not use the built-in methods, modern engines may not perform their best when they run this module.
So my proposal is to let them use what they know.

To fulfill both backward-compatibility and improvement for modern engines, it could be modified like below.
In this modification, I did not make any slowdown in the function code but in the module initialization.
i.e. I did not put the if-else thing in the leftPad function body.

Original

module.exports = leftPad;

Modified

if("padStart" in String.prototype)
{
  module.exports = function leftPad(str, num, ch) {
    return (str + '').padStart(num, ch);
    // The reason why you don't use `.toString()` would be
    // to deal with `null`s and `undefined`s, right?
  };
}
else
{
  module.exports = leftPad;
}

I was wondering if you could let me Pull-request this one.