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denoland-deno/core/examples/eval_js_value.rs
Ryan Dahl 1fb5858009
chore: update copyright to 2022 (#13306)
Co-authored-by: Erfan Safari <erfanshield@outlook.com>
2022-01-07 22:09:52 -05:00

48 lines
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Rust

// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
//! This example shows you how to evaluate JavaScript expression and deserialize
//! return value into a Rust object.
// NOTE:
// Here we are deserializing to `serde_json::Value` but you can
// deserialize to any other type that implementes the `Deserialize` trait.
use deno_core::v8;
use deno_core::JsRuntime;
use deno_core::RuntimeOptions;
fn main() {
let mut runtime = JsRuntime::new(RuntimeOptions::default());
// Evaluate some code
let code = "let a = 1+4; a*2";
let output: serde_json::Value =
eval(&mut runtime, code).expect("Eval failed");
println!("Output: {:?}", output);
let expected_output = serde_json::json!(10);
assert_eq!(expected_output, output);
}
fn eval(
context: &mut JsRuntime,
code: &str,
) -> Result<serde_json::Value, String> {
let res = context.execute_script("<anon>", code);
match res {
Ok(global) => {
let scope = &mut context.handle_scope();
let local = v8::Local::new(scope, global);
// Deserialize a `v8` object into a Rust type using `serde_v8`,
// in this case deserialize to a JSON `Value`.
let deserialized_value =
serde_v8::from_v8::<serde_json::Value>(scope, local);
match deserialized_value {
Ok(value) => Ok(value),
Err(err) => Err(format!("Cannot deserialize value: {:?}", err)),
}
}
Err(err) => Err(format!("Evaling error: {:?}", err)),
}
}