Interaction with Javascript

Calling Javascript functions

If you have Javascript functions in your app, you can call them from seed code using wasm_bindgen. For a detailed example, see the official example.

For example, you might have a Javascript function defined elsewhere in your document, like this:

<script type="text/javascript">
    function addOne(val) {
        return val + 1

<section id="app"></section>
<script type="module">
    import init from '/static/pkg/mypage.js';

Define a function like this in your app, where addOne here is the same name as the javascript function you wish to call.

/// Allows calling the JS function getCookie, for CSRF tokens.
extern "C" {
    fn addOne(val: &i32) -> i32;

You can then call this anywhere in your app, eg:

h1![ format!("Two plus one equals {}", addOne(2)) ]

For more info, reference this wasm-bindgen example.