How to use google closure with exported symbols?

2.1k Views Asked by Lin Z At 04 April 2025 at 22:19

Step 1: I create a test.js:

var Helloworld = function()
{
console.log("Hi..");
}

goog.exportSymbol('Helloworld', Helloworld);

Step 2: I compile the above javascript file using closure compiler：

java -jar ../compiler.jar --compilation_level ADVANCED_OPTIMIZATIONS --js test.js   --js_output_file test_out.js

I can see the content of test_out.js：

goog.a("Helloworld",function(){console.log("Hi..")});'

I don't know what is the meaning of "goog.a".

Step 3: I create a test.html:

<html>
<head><title>Hello World</title></head>
<body>
<script src="closure-library/closure/goog/base.js"></script>
<script src="test_out.js"></script>
 <script>
    var v = new Helloworld();
  </script>
</body>
</html>

Step 4: Load the html in the browser.

However, the Helloworld symbol cannot be found. What's wrong with my script to compile the javascript file? I'll appreciate if anyone can help. The document and tutorial of google closure is not very straightforward.

Original Q&A

There are 2 best solutions below

Chad Killingsworth On 11 December 2013 at 14:57

Closure-library is designed to be compiled with your source to make full use of dead code elimination. What you are missing is the correct library source files in your compilation command:

java -jar ../compiler.jar --compilation_level ADVANCED_OPTIMIZATIONS
    --js test.js --js closure-library/base.js
    --js_output_file test_out.js

The above command will only include the functions defined in the base.js file of closure library (which includes goog.exportSymbol). When compiled, your test_out.js will include the compiled definition of goog.exportSymbol.

For more advanced usage of closure-library, you'll need to make proper use of goog.require calls and use Closure-builder to resolve dependencies.

user2987263 On 13 November 2013 at 10:47

In your test.html, have you tried replacing:

<script>
    var v = new Helloworld();
</script>

with

<script>
    var Helloworld = goog.getObjectByName('Helloworld');
    var v = new Helloworld();
</script>

How to use google closure with exported symbols?

There are 2 best solutions below

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