Use functions defined in ES6 module directly in html

问题

I am trying to accomplish a pretty simple thing: I have some code on a javascript module file and I import it on another javascript file (that doesn't export anything) and I want to call some of the defined functions in that file from the HTML directly.

Let's se some representative and minimal example of what's happening to me (actually tested the code and gives the exact same issue I'm experiencing with the real one, which is not really much more complex than this one):

module.js:

const mod = () => 'Hello there!';
export { mod };

main.js:

import { mod } from './module.js';

function hello()
{
    console.log(mod());
}

main.html:

<!DOCTYPE html>
<html>
    <head>
        <script type="module" src="module.js"></script>
        <script type="module" src="main.js"></script>
    </head>

    <body>
        <button name="next-button" onclick="hello()">Obi-Wan abandons the high ground to salute you</button>
    </body>
</html>

Without the import (and putting all the function definitions on a single .js file) I can call the function directly from the HTML. However, once I have introduced the modules I am no longer able to: it simply says that the "hello()" function is not defined.

I am completely new to ES6 modules (and to front-end javascript in fact), so I am fully aware all I just said is just lack of knowledge (or understanding), but I would appreciate any comment on what am I doing wrong and how to solve it so I can have my code in different files and be able to use it. Thank you all in advance!

回答1:

Each module has its own scope. They are not sharing the global scope like "normal" scripts do. That means hello is only accessible inside the main.js module/file itself.

If you explicitly want to create a global variable, you can achieve that by creating a property on the global object, window:

function hello()
{
    console.log(mod());
}
window.hello = hello;

See also Define global variable in a JavaScript function

Having said that, it's good practice to avoid global variables. Instead you can restructure the HTML to load the modules after the button was created and bind the event handler via JavaScript:

<!DOCTYPE html>
<html>
    <body>
        <button name="next-button">Obi-Wan abandons the high ground to salute you</button>
        <script type="module" src="module.js"></script>
        <script type="module" src="main.js"></script>
    </body>
</html>

and

import { mod } from './module.js';

function hello()
{
    console.log(mod());
}
document.querySelector('button').addEventListener('click', hello);

来源：https://stackoverflow.com/questions/53630310/use-functions-defined-in-es6-module-directly-in-html

标签

javascript

html

es6-modules