Big O of javascript built-in split function

Question

Example:

var string = "abcde";
var array = string.split("");
// array = ["a", "b", "c", "d", "e"]

What is the amortized running time of this split function? Also, how do I view source code of such built-in functions in javascript?

Answer 1

With an empty delimiter argument, split is essentially equivalent to:

var len = string.length;
var result = Array(len)
for (i = 0; i < len; i++) {
    result[i] = string[i];
}

This is O(len) .

With a delimiter, it becomes O(string.length * delimiter.length) , because at each step in the loop it has to test whether there's a match for delimiter .

Answer 2

It's not very straightforward. The complexity will depend on the delimiter(whether it is a string or a regex). For every iteration, the string is searched for a match on the delimiter. The big O will essentially be O(len * big O of search algorithm) where len is the number of substrings.

Answer 3

EDIT: The OP did ask " What is the amortized running time of this split function? ". This is an answer to this precise question

To get the real running time of a function, see : How to measure time taken by a function to execute

var start = new Date().getTime();

for (i = 0; i < 50000; ++i) {
// do something
}

var end = new Date().getTime();
var time = end - start;
alert('Execution time: ' + time);

You can't view JS source code, as it's built-in each navigator. You can take a look at Chromium project , maybe you'll find what you are looking for.

I don't know how to get the amortized time of the split, and I dont think you can calculate it without having access to source code.