How can I load my own js module with goog.provide

2019-02-04 15:33发布

站内问答 / JavaScript
529 7 4

We are trying to switch the packaging for our project from dojo to google closure, but we haven't had any luck so far. Here is a simple example that illustrates what we are trying to accomplish:


<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <script type="text/javascript" src="runtime/src/core/lib/goog-rev26/base.js"></script>
        <script>
            goog.require("foo.bar");
            function main() {foo.bar.echo("hello world")}
        </script>
    </head>
<body onload="main()">
</body>
</html>

Then in /foo/bar.js I have:


goog.provide("foo.bar");
foo.bar.echo = function(s) {console.debug(s);}

The errors I receive in firebug are as follows:

goog.require could not find: foo.bar
foo is not defined

When I look in the Net tab, there isn't an http request out to fetch a file - I was expecting the closure library to generate a script tag to fetch bar.js.

help! ;)

7条回答
Luminary・发光体
2楼-- · 2019-02-04 16:23

I figured it out and it's not very hard, but there are a few gotchas.

Basically, you can use the dependency generating script calcdeps.py (you should read calcdeps.py docs) in one of several modes:

  1. Generating deps.js file
  2. Concatenating everything into a single file, optionally compiling it using the closure compiler.

For development you should use (1), since it allows you to not run the calcdeps.py after editing the JS sources, unless you make changes to the dependency tree. The rest of the answer is about this way, I haven't tried the other one yet.

Here's what I did to generate it:

#!/bin/bash
cd closure-library/closure/goog
python ../bin/calcdeps.py -p ../../../js -o deps > ../../../my-deps.js

...assuming the following directory structure:

project/
  closure-library/ (as checked out from SVN)
  js/ (my JS code)
  app.html

(the -p parameter traverses all js files in the specified directory and the docs say you can specify multiple directories to search if you have to.)

The above call creates a my-deps.js file next to the main app.html, which I use to run the application. The created file contains information about my JS files in js/ and looks like this:

goog.addDependency('../../../js/controllers.js', ['proj.controllers'], []);
goog.addDependency('../../../js/ui.js', ['proj.ui'], ['proj.controllers']);

- where the first string it the path to my JS file relative to closure-library/closure/goog/base.js (this is important!), the second array is the list of goog.provide-d strings, and the last array is the list of goog.require-d strings.

Now in app.html I have:

<script src="closure-library/closure/goog/base.js"></script>
<script src="my-deps.js"></script>
<script>
  goog.require("proj.ui");
</script>
<script>
  // here we can use the required objects
</script>

Note:

  1. In addition to including closure's base.js, I include my generated deps.js
  2. As mentioned in the tutorial the goog.require call has to be in a separate script tag, because it appends a script tag to load the required scripts and they are loaded after the current script tag finished processing.

Gotchas:

  1. The described above issue with paths being relative to base.js. goog.require creates the script URL to load by concatenating the base.js base URL (i.e. without base.js leafname) and the first parameter to goog.addDependency in deps.js.
  2. calcdeps.py doesn't work well on Windows, in particular using the backslashes in the deps.js string literals
  3. If something doesn't work well, you may want to look through all issues mentioning calcdeps and make sure you have an up to date checkout.
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