5 ms·

We have. I spent some time optimizing [0] a String.repeat function over at Stackoverflow and I was surprised that many developers today don't know what they are

by nikolay 11y ago

We have. I spent some time optimizing [0] a String.repeat function over at Stackoverflow and I was surprised that many developers today don't know what they are doing, including core team members [1]. Specifically, function repeatString(str, len) { return Array.apply(null, { length: len + 1 }).join(str).slice(0, len) } [0]: http://stackoverflow.com/questions/202605/repeat-string-javascript/36173160#36173160 http://stackoverflow.com/questions/202605/repeat-string-java... [1]: http://stackoverflow.com/questions/202605/repeat-string-javascript/35319469#35319469 http://stackoverflow.com/questions/202605/repeat-string-java...

Macha 11y ago
So I don't think this is an example of core team members who don't know what you're doing. This function repeats a string up to a certain length. e.g. repeatString(foo, 10) = foofoofoof This could entirely be what the developers needed in their code base. The fact that it doesn't repeat a string N times, is at best, an example of bad naming. The issue here is that someone unrelated to the core team grepped the node codebase for the term they wanted and threw a function up as a SO answer without understanding what it did.
- nikolay 11y ago
  Allocate and join an array of blanks just to repeat a string is acceptable?!
  - Macha 11y ago
    I guess I'm also as guilty of looking at input/output rather than implementation here.
    - nikolay 11y ago
      Here's a benchmark [0]! [0]: https://jsfiddle.net/nikolay/Lgshxrk8/ https://jsfiddle.net/nikolay/Lgshxrk8/
  - jestar_jokin 11y ago
    Joining an array of strings is sometimes better than concatenating a string in place, yes. Consider the following: 1: var str = 'foo'; 2: str += 'bar'; 3: str += 'baz'; At program load, you have three string constants, 'foo', 'bar', and 'baz'. At 1, 'str' becomes a pointer to the string constant 'foo'. At 2, 'str' becomes a pointer to a string 'foobar'. Memory is allocated to store this string. At 3, 'str' becomes a pointer to a stinrg 'foobarbaz'. Memory is allocated to store this string. Now consider the following: 1: var str = ['foo', 'bar', 'baz'].join(''); At program load, you have three string constants, 'foo', 'bar', and 'baz'. At 1, 'str' becomes a pointer to the string constant 'foobarbaz'. In the array concatenation, the JS interpreter can create a single string buffer large enough to contain the contents of each array element and the separator string * N - 1 (where N is the number of elements), and return a pointer. Once you have a large number of elements, or are joining large strings, the performance difference (especially regarding garbage collection) could matter.
    - nikolay 11y ago
      You'll be surprised, but my implementation is, roughly speaking, 10 (Chrome) to 100 (Safari) to 200 (Firefox) times faster [0], depending on the browser! [0]: https://jsfiddle.net/nikolay/Lgshxrk8/ https://jsfiddle.net/nikolay/Lgshxrk8/
deleted 11y ago
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by nikolay 11y ago

Macha 11y ago

So I don't think this is an example of core team members who don't know what you're doing. This function repeats a string up to a certain length. e.g. repeatString(foo, 10) = foofoofoof This could entirely be what the developers needed in their code base. The fact that it doesn't repeat a string N times, is at best, an example of bad naming. The issue here is that someone unrelated to the core team grepped the node codebase for the term they wanted and threw a function up as a SO answer without understanding what it did.

nikolay 11y ago
Allocate and join an array of blanks just to repeat a string is acceptable?!
- Macha 11y ago
  I guess I'm also as guilty of looking at input/output rather than implementation here.
  - nikolay 11y ago
    Here's a benchmark [0]! [0]: https://jsfiddle.net/nikolay/Lgshxrk8/ https://jsfiddle.net/nikolay/Lgshxrk8/
- jestar_jokin 11y ago
  Joining an array of strings is sometimes better than concatenating a string in place, yes. Consider the following: 1: var str = 'foo'; 2: str += 'bar'; 3: str += 'baz'; At program load, you have three string constants, 'foo', 'bar', and 'baz'. At 1, 'str' becomes a pointer to the string constant 'foo'. At 2, 'str' becomes a pointer to a string 'foobar'. Memory is allocated to store this string. At 3, 'str' becomes a pointer to a stinrg 'foobarbaz'. Memory is allocated to store this string. Now consider the following: 1: var str = ['foo', 'bar', 'baz'].join(''); At program load, you have three string constants, 'foo', 'bar', and 'baz'. At 1, 'str' becomes a pointer to the string constant 'foobarbaz'. In the array concatenation, the JS interpreter can create a single string buffer large enough to contain the contents of each array element and the separator string * N - 1 (where N is the number of elements), and return a pointer. Once you have a large number of elements, or are joining large strings, the performance difference (especially regarding garbage collection) could matter.
  - nikolay 11y ago
    You'll be surprised, but my implementation is, roughly speaking, 10 (Chrome) to 100 (Safari) to 200 (Firefox) times faster [0], depending on the browser! [0]: https://jsfiddle.net/nikolay/Lgshxrk8/ https://jsfiddle.net/nikolay/Lgshxrk8/

deleted 11y ago

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