# serde-wasm-bindgen **Repository Path**: mirrors_cloudflare/serde-wasm-bindgen ## Basic Information - **Project Name**: serde-wasm-bindgen - **Description**: Native integration of Serde with wasm-bindgen - **Primary Language**: Unknown - **License**: MIT - **Default Branch**: main - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 0 - **Created**: 2020-08-08 - **Last Updated**: 2026-02-28 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README [![Crates.io](https://img.shields.io/crates/d/serde-wasm-bindgen?logo=rust)](https://crates.io/crates/serde-wasm-bindgen) [![docs.rs](https://img.shields.io/docsrs/serde-wasm-bindgen)](https://docs.rs/serde-wasm-bindgen/) [![GitHub Sponsors](https://img.shields.io/github/sponsors/rreverser)](https://github.com/sponsors/RReverser) This is a native integration of [Serde](https://serde.rs/) with [wasm-bindgen](https://github.com/rustwasm/wasm-bindgen). It allows to convert Rust data types into native JavaScript types and vice versa. Initially this library was created while working for [@Cloudflare](https://github.com/cloudflare) as [an alternative implementation](https://github.com/rustwasm/wasm-bindgen/issues/1258) to the JSON-based Serde support built into the `wasm-bindgen` but, [nowadays](https://github.com/rustwasm/wasm-bindgen/pull/3031) `serde-wasm-bindgen` is the officially preferred approach. It provides much smaller code size overhead than JSON, and, in most common cases, provides much faster serialization/deserialization as well. ## Usage Copied almost verbatim from the [`wasm-bindgen` guide](https://rustwasm.github.io/wasm-bindgen/reference/arbitrary-data-with-serde.html#serializing-and-deserializing-arbitrary-data-into-and-from-jsvalue-with-serde): ### Add dependencies To use `serde-wasm-bindgen`, you first have to add it as a dependency in your `Cargo.toml`. You also need the `serde` crate, with the `derive` feature enabled, to allow your types to be serialized and deserialized with Serde. ```toml [dependencies] serde = { version = "1.0", features = ["derive"] } serde-wasm-bindgen = "0.6" ``` ### Rust usage ```rust use std::collections::HashMap; use serde::{Serialize, Deserialize}; use wasm_bindgen::prelude::*; // Add `#[derive(Serialize, Deserialize)]` to your types. #[derive(Serialize, Deserialize)] pub struct Example { pub field1: HashMap, pub field2: Vec>, pub field3: [f32; 4], } // Send values to JavaScript with `serde_wasm_bindgen::to_value`. #[wasm_bindgen] pub fn send_example_to_js() -> Result { let mut field1 = HashMap::new(); field1.insert(0, String::from("ex")); let example = Example { field1, field2: vec![vec![1., 2.], vec![3., 4.]], field3: [1., 2., 3., 4.] }; Ok(serde_wasm_bindgen::to_value(&example)?) } // Receive values from JavaScript with `serde_wasm_bindgen::from_value`. #[wasm_bindgen] pub fn receive_example_from_js(val: JsValue) -> Result<(), JsValue> { let example: Example = serde_wasm_bindgen::from_value(val)?; /* …do something with `example`… */ Ok(()) } ``` ### JavaScript Usage In the value received by JavaScript, `field1` will be a `Map`, `field2` will be an `Array>`, and `field3` will be an `Array`. ```js import { send_example_to_js, receive_example_from_js } from "example"; // Get the example object from wasm. let example = send_example_to_js(); // Add another "Vec" element to the end of the "Vec>" example.field2.push([5, 6]); // Send the example object back to wasm. receive_example_from_js(example); ``` ## Supported Types Note that, even though it might often be the case, by default this library doesn't attempt to be strictly compatible with JSON, instead prioritising better compatibility with common JavaScript idioms and representations. If you need JSON compatibility (e.g. you want to serialize `HashMap` as plain objects instead of JavaScript `Map` instances), use the [`Serializer::json_compatible()`](https://docs.rs/serde-wasm-bindgen/latest/serde_wasm_bindgen/struct.Serializer.html#method.json_compatible) preset. By default, Rust ⬄ JavaScript conversions in `serde-wasm-bindgen` follow this table: | Rust | JavaScript | Also supported in `from_value` | |-----------------------------------|--------------------------------------|--------------------------------| | `()` and `Option::None` | `undefined` | `null` | | `bool` | `boolean` | | | `f32`, `f64` | `number` | | | `u8`, `i8`, …, `u32`, `i32` | `number` in the [safe integer] range | | | `u64`, `i64`, `usize`, `isize` | `number` in the [safe integer] range | `bigint` | | `u128`, `i128` | `bigint` | | | `String` | `string` | | | `char` | single-codepoint `string` | | | `Enum::Variant { … }` | [as configured in Serde] | | | `HashMap`, `BTreeMap`, etc. | `Map` | any iterable over `[K, V]` | | `Struct { key1: value1, … }` | `{ key1: value1, … }` object | | | tuple, `Vec`, `HashSet`, etc. | `T[]` array | any iterable over `T` | | [`serde_bytes`] byte buffer | `Uint8Array` | `ArrayBuffer`, `Array` | [as configured in Serde]: https://serde.rs/enum-representations.html [safe integer]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isSafeInteger [`serde_bytes`]: https://github.com/serde-rs/bytes The first two columns show idiomatic representations on Rust and JavaScript sides, while the 3rd column shows which JavaScript values are additionally supported when deserializing from JavaScript to the Rust type. ### Serializer configuration options You can customize serialization from Rust to JavaScript by setting the following options on the [`Serializer::new()`](https://docs.rs/serde-wasm-bindgen/latest/serde_wasm_bindgen/struct.Serializer.html) instance (all default to false): - `.serialize_missing_as_null(true)`: Serialize `()`, unit structs and `Option::None` to `null` instead of `undefined`. - `.serialize_maps_as_objects(true)`: Serialize maps into plain JavaScript objects instead of ES2015 Maps. - `.serialize_large_number_types_as_bigints(true)`: Serialize `u64`, `i64`, `usize` and `isize` to `bigint`s instead of attempting to fit them into the [safe integer] `number` or failing. - `.serialize_bytes_as_arrays(true)`: Serialize bytes into plain JavaScript arrays instead of ES2015 Uint8Arrays. You can also use the `Serializer::json_compatible()` preset to create a JSON compatible serializer. It enables `serialize_missing_as_null`, `serialize_maps_as_objects`, and `serialize_bytes_as_arrays` under the hood. ### Preserving JavaScript values Sometimes you want to preserve original JavaScript value instead of converting it into a Rust type. This is particularly useful for types that can't be converted without losing the data, such as [`Date`](https://docs.rs/js-sys/latest/js_sys/struct.Date.html), [`RegExp`](https://docs.rs/js-sys/latest/js_sys/struct.RegExp.html) or 3rd-party types. `serde_wasm_bindgen::preserve` allows you to do just that: ```rust use serde::{Serialize, Deserialize}; #[derive(Serialize, Deserialize)] pub struct Example { pub regular_field: i32, #[serde(with = "serde_wasm_bindgen::preserve")] pub preserved_date: js_sys::Date, #[serde(with = "serde_wasm_bindgen::preserve")] pub preserved_arbitrary_value: wasm_bindgen::JsValue, } ``` ## TypeScript support There's no built-in type generation in this crate, but you can [tsify](https://github.com/madonoharu/tsify) with the `js` feature which integrates with `serde-wasm-bindgen` under the hood. Aside from generating structural typings, it also allows to derive `IntoWasmAbi` / `FromWasmAbi` so that you don't have to write `from_value` / `to_value` by hand. ## License Licensed under the MIT license. See the [LICENSE](https://github.com/RReverser/serde-wasm-bindgen/blob/master/LICENSE) file for details.