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Asked: 2026-05-20T23:46:33+00:00

We are creating a javascript library from scratch and we need some utilities functions,

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We are creating a javascript library from scratch and we need some utilities functions, just like what dojo provides, e.g. xhr wrapper, simple inheritances and array manipulation, etc. We don’t want to write these functions ourselves from scratch, but we also don’t want to just copy and paste code from dojo.

Dojo provides the custom build mechanism, but it works on the module level. For example, in the custom build, you can specify to only add the lang module in the dojo base. But we may only need the dojo.hitch function in the lang module, but not the dojo.clone function that also included in the lang module. We have a tight constraint on the size of the library file, so we need to remove any unused code.

What we are seeking is a way to extract certain functions from a module and build these functions into a single javascript file. For example, say we need dojo.mixin, dojo.declare and dojo.hitch functions, then these functions’ declaration and their dependent inner functions should be built into a single file.

Any suggestions?

Update from my test result

Thanks Stephen Chung for your great suggestion on how to solve this problem.

So basically I created a custom dojo build with four modules : dojo._base.xhr, dojo._base.json, dojo._base.declare and dojo._base.lang. The built dojo.js file is 149kb, after using Google Closure compiler with advanced mode, the size has reduced to 24kb and the unused functions have been removed. If we want to keep some functions, just add another javascript file like below:

window['dojo'] = dojo;
window['dojo']['requireLocalization'] = dojo.requireLocalization;
window['dojo']['moduleUrl'] = dojo.moduleUrl;

and compile it with dojo.js.

Unfortunately the size is still a little bigger. We have a size limit of 40k in total. But this is still a very good solution for other cases.

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1 Answer

  1. Editorial Team

    Dojo Core is written in a very compact manner, with a lot of cross callings (i.e. one function calling other functions) in order to save download bytes and reduce code size.

    Therefore, you need a minimal set of Dojo Core functions, together with the functions that it calls.

    In other words, what you need is a build that includes Dojo Core, but then removes any dead-code that is never called.

    I’d suggest that you don’t go about creating a minimal-footprint library by writing it from scratch yourself. What you need is to use the Closure Compiler’s Advanced Mode to process your Dojo application. It removes dead code, optimizes the entire app, and fully obfuscates it.

    And yes, it is possible to use the Closure Compiler with Dojo in Advanced Mode — Dojo is probably the only popular library that can do it. Read it here.

    Some statistics: A Closure-compiled Dojo app is typically around 25-30% smaller than the equivalent Dojo app in a Shrinksafe build. It depends on how many Dojo Core features you use — typically you may reduce Dojo Core up to 40% of the original size (i.e. reduce code size by up to 60%) from dead code removal alone. Further reductions are more difficult, as you may have to start removing features like the Dojo loader etc.

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