I am building a string to be parsed into an array by JavaScript. I can make it delimited or I can make the fields fixed-width.
I have only tested on Windows with Firefox and Chrome, so please run the test from other OSes and browsers. My two test results are clear: String.prototype.split() is the winner by a large margin.
Is my fixed-width code not efficient enough, or is the built-in string split function simply superior? Is there a way to code it so that the fixed-width parsing triumphs? If this was C/C++, the fixed-width code, written properly, would be the clear winner. But I know JavaScript is an entirely different beast.
String.prototype.split() is a built-in JavaScript function. Expect it to be highly optimized for the particular JS engine and be written not in JavaScript but in C++.
It should thus not come a surprise that you can't match its performance with pure JavaScript code.
String operations like splitting a delimited string are inherently memory-bound. Hence, knowing the location of delimiters doesn't really help much, since the entire string still needs to be traversed at least once (to copy the delimited fragments). Fixed-position splitting might be faster for strings that exceed D-cache size, but your string is just 13KB long, so traversing it multiple times isn't going to matter.