When comparing Bazel vs Jam, the Slant community recommends Bazel for most people. In the question“What are the best open-source build systems for C/C++?” Bazel is ranked 8th while Jam is ranked 15th. The most important reason people chose Bazel is:
Builds only use input files that are explicitly declared in the build specification. On Linux, Bazel runs tools in a sandboxed environment that contain only the minimum necessary files required.
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Pros
Pro Correct and repeatable builds
Builds only use input files that are explicitly declared in the build specification. On Linux, Bazel runs tools in a sandboxed environment that contain only the minimum necessary files required.
Pro Fast even at scale
Even at large scale it's pretty fast (it's based on what Google uses internally for their huge code base).
Pro Can rule shell commands
Pro Handles mixed language builds
Pro High level build descriptions
Pro Build rule errors are informative
When builds fail because of an issue in the build rules, the errors provided are usually very informative and helpful to resolve the issue.
Pro Good IDE support
Pro Standard protocol for remote execution and caching
Pro Remote execution of commands
Pro Has a central package repository
A central repository provides more guarantees about the availability of the package. With requiring directly from repository urls, the entire project could potentially be taken down on a whim.
Pro Community is focused on client side javascript
Because Jam only manages Javascript and only works on the client side, you have the assurance that any packages listed are AMD compatible for asynchronous loading.
Pro Architecture independent
Jam's only a front-end package manager, the rest of your server can be on a different architecture or framework. No matter what the architecture, Jam will integrate easily with it.
Pro Provides the best AMD compatibility allowing for better asynchronous loading
Jam requires AMD (Asynchronous Module Definition), which means faster package loading, as it can be done asynchronously.
Cons
Con Draconian sandboxing, explicit inputs requirement
Requirement to explicitly name all inputs disqualifies Bazel for many workflows, e.g. those relying on tools that scan a directory tree themselves looking for files to process. Sandboxing as implemented in Bazel imposes further restrictions. If a command is successful when you type it in the shell, it should also be successful when pasted verbatim into a rule, but with Bazel it very often isn't.
Con Confusing for beginners
With so many capabilities, trying to implement with a simple project is overkill and unpleasant.
Con Forced AMD compatibility means fewer libraries
AMD is currently not as popular as CommonJS modules, which means if a library isn't supported, you'll have to deal with it yourself.