3 ms·

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/