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wasm-bindgen/guide/src/reference/attributes/on-js-imports/static_method_of.md
Alex Crichton 0b1a764f8a
Guarantee static_method_of uses the right this (#1795) 
This came up during #1760 where `Promise.resolve` must be invoked with
`this` as the `Promise` object, but we were erroneously importing it in
such a way that it didn't have a shim and `this` was `undefined`.
2019-09-26 12:33:04 -05:00

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static_method_of = Blah

The static_method_of attribute allows one to specify that an imported function is a static method of the given imported JavaScript class. For example, to bind to JavaScript's Date.now() static method, one would use this attribute:

#[wasm_bindgen]
extern "C" {
    type Date;

    #[wasm_bindgen(static_method_of = Date)]
    pub fn now() -> f64;
}

The now function becomes a static method of the imported type in the Rust bindings as well:

let instant = Date::now();

This is similar to the js_namespace attribute, but the usage from within Rust is different since the method also becomes a static method of the imported type. Additionally this attribute also specifies that the this parameter when invoking the method is expected to be the JS class, e.g. always invoked as Date.now() instead of const x = Date.now; x().