Slicing & Trimming

These all return another str — a sub-range of the same backing string, with no characters copied.

slice

slice(start, end?) — like String#slice, including negative indices (counted from the end) and an out-of-order range collapsing to empty.

const v = str.from("the quick brown fox");
v.slice(4, 9).toString(); // "quick"
v.slice(-3).toString(); // "fox"
v.slice(10, 4).toString(); // "" (end < start)

str.slice("the quick brown fox", 4, 9); // free-function form

substring

substring(start, end?) — like String#substring: negatives clamp to 0, and arguments swap if start > end.

str.from("the quick").substring(10, 4).toString(); // "quick" (swapped)

substr

substr(start, length?) — like String#substr: a start (negative counts from the end) and a length.

str.from("the quick brown fox").substr(4, 5).toString(); // "quick"

charAt / at

Both return a one-unit view (or an empty view when out of range). charAt takes a non-negative index; at allows negatives.

const v = str.from("hello");
v.charAt(0).toString(); // "h"
v.at(-1).toString(); // "o"
v.charAt(99).toString(); // "" (out of range)

For a code-unit value rather than a view, use charCodeAt or the [] operator — both allocation-free.

trim, trimStart, trimEnd

Whitespace is trimmed by moving the view's bounds inward — the result shares the original bytes. trimLeft / trimRight are aliases for trimStart / trimEnd.

const v = str.from("  hello  ");
v.trim().toString(); // "hello"
v.trimStart().toString(); // "hello  "
v.trimEnd().toString(); // "  hello"

The whitespace set matches AssemblyScript's String#trim (ASCII whitespace plus the Unicode space separators, line/paragraph separators, NBSP, BOM, …).

split

split(separator, limit?) returns a str[] of zero-copy pieces — you pay for a copy only on the pieces you materialize. An empty separator splits into single-unit views; limit caps the number of pieces.

const f = str.split("a,bb,ccc", ","); // [str, str, str]
f[1].toString(); // "bb"

str.split("a,b,c,d", ",", 2).length; // 2

A tokenizer that never allocates until it finds what it wants:

const parts = str.split("id,name,email,role", ",");
for (let i = 0; i < parts.length; i++) {
  if (parts[i].equalsString("email")) {
    /* found field i — still zero-copy */
  }
}