I am trying to optimize a function which does binary search of strings in JavaScript.

Binary search requires you to know whether the key is == the pivot or < the pivot.

But this requires two string comparisons in JavaScript, unlike in C like languages which have the strcmp() function that returns three values (-1, 0, +1) for (less than, equal, greater than).

Is there such a native function in JavaScript, that can return a ternary value so that just one comparison is required in each iteration of the binary search?

8

3 Answers

You can use the localeCompare() method. 

string_a.localeCompare(string_b); /* Expected Returns: 0: exact match -1: string_a < string_b 1: string_a > string_b */

Further Reading:

11

Well in JavaScript you can check two strings for values same as integers so yo can do this:

  • "A" < "B"
  • "A" == "B"
  • "A" > "B"

And therefore you can make your own function that checks strings the same way as the strcmp().

So this would be the function that does the same:

function strcmp(a, b) { return (a<b?-1:(a>b?1:0)); }
2

You can use the comparison operators to compare strings. A strcmp function could be defined like this:

function strcmp(a, b) { if (a.toString() < b.toString()) return -1; if (a.toString() > b.toString()) return 1; return 0; }

Edit    Here’s a string comparison function that takes at most min { length(a), length(b) } comparisons to tell how two strings relate to each other:

function strcmp(a, b) { a = a.toString(), b = b.toString(); for (var i=0,n=Math.max(a.length, b.length); i<n && a.charAt(i) === b.charAt(i); ++i); if (i === n) return 0; return a.charAt(i) > b.charAt(i) ? -1 : 1; }
8