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str ​

str gives AssemblyScript virtual, zero-copy strings.

A str is a view into an existing string: a reference to the backing string (so the GC keeps it alive) plus a [start, end) pair of raw byte pointers into that data. Slicing, trimming, and searching just move the two pointers — no characters are copied until you ask for a real string back with .toString().

It ships as a single class with the full native String surface, so it reads like string but allocates only at the boundary where you actually need an owned string.

ts
import { str } from "as-str";

const real: string = "GET /index.html 200 1043";
const method = str.slice(real, 0, 3); // "GET" — a view, no allocation
method.toString(); // "GET" — materialized on demand

What you get ​

  • Views — slice, substring, substr, trim*, charAt, at, and split return another str; the backing bytes are never copied.
  • The full String surface — every native method, as both instance methods (v.indexOf(…)) and free functions (str.indexOf(s, …)).
  • Operators — ==, !=, <, <=, >, >=, +, and v[i] indexing.
  • Accelerated scans — indexOf / includes / compare run SWAR by default and SIMD when compiled with --enable simd.
  • Encoding — str.UTF8 / str.UTF16, a drop-in for String.UTF8 / String.UTF16, running off the view's pointer range.
  • GC-safe — a view keeps its backing string reachable; chains of views anchor to the original, never to intermediates.
  • str8 — a byte-indexed UTF-8 sibling (Rust/Go model) for data that is already UTF-8, plus callable str(x) / str8(x) converters.

Start here ​

  1. Getting Started — install and create your first view.
  2. The View Model — how a str works and when bytes are copied.
  3. str8 (UTF-8) — the byte-indexed UTF-8 view, and the converters.
  4. API — slicing, searching, transforming, comparison, encoding.
  5. Performance — SWAR/SIMD, and the numbers.
  6. Internals — the design, for contributors.

When to reach for it ​

Reach for str when you are tokenizing, parsing, or walking a large string and the intermediate slice/substring/trim copies dominate — a log-line splitter, a CSV/columnar reader, a protocol parser. You carry cheap windows into the original data and pay for a single copy only at the edge where an owned string leaves your code.

If you need fast JSON for AssemblyScript, see json-as; for testing your code, as-test.