Javascript 在字符串中的第 3 个字符后剪切字符串

Question

I need to write function that returns 3strings after character ', ' so if there is none or 1 or 2 or 3 to return empty string if ', ' character is found else return 3 strings...i wrote these function but it is very cpu intensive...can be shorter and faster code?

https://jsfiddle.net/1nfyq327/

    var str = 'AAA BBB CC., DD EE, FF FF, GG GG, HH HH, II II, JJ JJ, GG GG';

    var res = str.substring(0, str.indexOf(', ', str.indexOf(', ', str.indexOf(', ')+1)+1));

    console.log(res);

Result is:

AAA BBB CC., DD EE, FF FF

Result is fine but i need faster code because it will execute on low power cpu so speed is very cruicial...

Answer 1

In terms of speed there is not that much you can do.
The code you wrote runs in O(n) , which is the best possible time complexity for your problem.

You can play around with native functions ( split() , substring() ... that are implemented in c++ and therefore will run quickly) to see if one of them is faster, or rewrite it in pure javascript with a for loop. And compare the results.

In your case the best thing you can really do is write a little benchmark testing how fast your solution is and compare that. Althought there is high chance that there is something else in your code that runs slowly. :)

Answer 2

Use split , slice and join :

 var str = 'AAA BBB CC., DD EE, FF FF, GG GG, HH HH, II II, JJ JJ, GG GG'; var result = str.split(',').slice(0,3).join(','); console.log(result);

Answer 3

You could split with a limit of String#split and join the array.

 var string = 'AAA BBB CC., DD EE, FF FF, GG GG, HH HH, II II, JJ JJ, GG GG', result = string.split(',', 3).join(',') console.log(result);