Struct quickjs_rs::Context
source · pub struct Context { /* private fields */ }
Expand description
Context is a wrapper around a QuickJS Javascript context. It is the primary way to interact with the runtime.
For each Context
instance a new instance of QuickJS
runtime is created. It means that it is safe to use
different contexts in different threads, but each
Context
instance must be used only from a single thread.
Implementations§
source§impl Context
impl Context
sourcepub fn builder() -> ContextBuilder
pub fn builder() -> ContextBuilder
Create a ContextBuilder
that allows customization of JS Runtime settings.
For details, see the methods on ContextBuilder
.
let _context = quickjs_rs::Context::builder()
.memory_limit(100_000)
.build()
.unwrap();
sourcepub fn new() -> Result<Self, ContextError>
pub fn new() -> Result<Self, ContextError>
Create a new Javascript context with default settings.
Examples found in repository?
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pub fn main() {
let context = Context::new().unwrap();
let value = context.eval("1 + 2").unwrap();
println!("js: 1 + 2 = {:?}", value);
context
.add_callback("myCallback", |a: i32, b: i32| a + b * b)
.unwrap();
let value = context
.eval(
r#"
var x = myCallback(10, 20);
x;
"#,
)
.unwrap();
println!("js: callback = {:?}", value);
}
sourcepub fn reset(self) -> Result<Self, ContextError>
pub fn reset(self) -> Result<Self, ContextError>
Reset the Javascript engine.
All state and callbacks will be removed.
sourcepub fn eval(&self, code: &str) -> Result<JsValue, ExecutionError>
pub fn eval(&self, code: &str) -> Result<JsValue, ExecutionError>
Evaluates Javascript code and returns the value of the final expression.
Promises:
If the evaluated code returns a Promise, the event loop
will be executed until the promise is finished. The final value of
the promise will be returned, or a ExecutionError::Exception
if the
promise failed.
use quickjs_rs::{Context, JsValue};
let context = Context::new().unwrap();
let value = context.eval(" 1 + 2 + 3 ");
assert_eq!(
value,
Ok(JsValue::Int(6)),
);
let value = context.eval(r#"
function f() { return 55 * 3; }
let y = f();
var x = y.toString() + "!"
x
"#);
assert_eq!(
value,
Ok(JsValue::String("165!".to_string())),
);
Examples found in repository?
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pub fn main() {
let context = Context::new().unwrap();
let value = context.eval("1 + 2").unwrap();
println!("js: 1 + 2 = {:?}", value);
context
.add_callback("myCallback", |a: i32, b: i32| a + b * b)
.unwrap();
let value = context
.eval(
r#"
var x = myCallback(10, 20);
x;
"#,
)
.unwrap();
println!("js: callback = {:?}", value);
}
sourcepub fn eval_as<R>(&self, code: &str) -> Result<R, ExecutionError>where
R: TryFrom<JsValue>,
R::Error: Into<ValueError>,
pub fn eval_as<R>(&self, code: &str) -> Result<R, ExecutionError>where R: TryFrom<JsValue>, R::Error: Into<ValueError>,
Evaluates Javascript code and returns the value of the final expression as a Rust type.
Promises:
If the evaluated code returns a Promise, the event loop
will be executed until the promise is finished. The final value of
the promise will be returned, or a ExecutionError::Exception
if the
promise failed.
use quickjs_rs::{Context};
let context = Context::new().unwrap();
let res = context.eval_as::<bool>(" 100 > 10 ");
assert_eq!(
res,
Ok(true),
);
let value: i32 = context.eval_as(" 10 + 10 ").unwrap();
assert_eq!(
value,
20,
);
sourcepub fn set_global<V>(&self, name: &str, value: V) -> Result<(), ExecutionError>where
V: Into<JsValue>,
pub fn set_global<V>(&self, name: &str, value: V) -> Result<(), ExecutionError>where V: Into<JsValue>,
Set a global variable.
use quickjs_rs::{Context, JsValue};
let context = Context::new().unwrap();
context.set_global("someGlobalVariable", 42).unwrap();
let value = context.eval_as::<i32>("someGlobalVariable").unwrap();
assert_eq!(
value,
42,
);
sourcepub fn call_function(
&self,
function_name: &str,
args: impl IntoIterator<Item = impl Into<JsValue>>
) -> Result<JsValue, ExecutionError>
pub fn call_function( &self, function_name: &str, args: impl IntoIterator<Item = impl Into<JsValue>> ) -> Result<JsValue, ExecutionError>
Call a global function in the Javascript namespace.
Promises:
If the evaluated code returns a Promise, the event loop
will be executed until the promise is finished. The final value of
the promise will be returned, or a ExecutionError::Exception
if the
promise failed.
use quickjs_rs::{Context, JsValue};
let context = Context::new().unwrap();
let res = context.call_function("encodeURIComponent", vec!["a=b"]);
assert_eq!(
res,
Ok(JsValue::String("a%3Db".to_string())),
);
sourcepub fn add_callback<F>(
&self,
name: &str,
callback: impl Callback<F> + 'static
) -> Result<(), ExecutionError>
pub fn add_callback<F>( &self, name: &str, callback: impl Callback<F> + 'static ) -> Result<(), ExecutionError>
Add a global JS function that is backed by a Rust function or closure.
The callback must satisfy several requirements:
- accepts 0 - 5 arguments
- each argument must be convertible from a JsValue
- must return a value
- the return value must either:
- be convertible to JsValue
- be a Result<T, E> where T is convertible to JsValue if Err(e) is returned, a Javascript exception will be raised
use quickjs_rs::{Context, JsValue};
let context = Context::new().unwrap();
// Register a closue as a callback under the "add" name.
// The 'add' function can now be called from Javascript code.
context.add_callback("add", |a: i32, b: i32| { a + b }).unwrap();
// Now we try out the 'add' function via eval.
let output = context.eval_as::<i32>(" add( 3 , 4 ) ").unwrap();
assert_eq!(
output,
7,
);
Examples found in repository?
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pub fn main() {
let context = Context::new().unwrap();
let value = context.eval("1 + 2").unwrap();
println!("js: 1 + 2 = {:?}", value);
context
.add_callback("myCallback", |a: i32, b: i32| a + b * b)
.unwrap();
let value = context
.eval(
r#"
var x = myCallback(10, 20);
x;
"#,
)
.unwrap();
println!("js: callback = {:?}", value);
}