eshost-cli

eshost-cli

eshost-cli makes it easy to run and compare ECMAScript code uniformly across a number of runtimes. Support for runtimes is provided by the library eshost. Every host is initialized with the eshost runtime API available which provides a uniform way to print, create realms, and eval code.

See eshost's supported hosts for a list of hosts, download/build locations, and other information.

Usage

See --help output for the full details. Basic usage:

• Add hosts using eshost --add <host name> <host type> <host path> --args <optional arguments>.
• Automatically configure jsvu-installed hosts using eshost --configure-jsvu.
• Evaluate a single expression using -e: eshost -e "[1,2,3].length".
• Execute a multi-statement program using -x: eshost -x "foo = 42; print(foo);"
• Execute a script using eshost path/to/script.js.
• Execute an expression or multi-statement program as module code using -m:
  • eshost -me "foo = 42" (this example should result in errors!)
  • eshost -mx "foo = 42; print(foo);" (this example should result in errors!)
• Execute a source file as module code by saving the file with an .mjs extension: eshost file.mjs; or by using the -m option: eshost -m file.js

Examples

$ npm install -g eshost-cli
$ eshost --help
$ eshost --add <name> <type> <path to host executable> --args <optional arguments>
$ eshost -e "Map.length"

## chakra-es6
0

## d8
0

## chakra
0

## spidermonkey
1

## node
0

$ eshost --configure-jsvu --jsvu-prefix jsvu
$ eshost --tags jsvu-web -itsx "let a = 40+2; print(a)"

## Source
let a = 40+2; print(a)

┌──────────┬────┐
│ jsvu-ch  │ 42 │
│ jsvu-jsc │    │
│ jsvu-sm  │    │
│ jsvu-v8  │    │
└──────────┴────┘

Managing Hosts

You can --list, --add, --edit, and --delete hosts. Adding a host requires a name, type, and path to the runtime executable. You can optionally pass arguments using --args. The same host can be added multiple times with different --args which makes it easy to compare the output of runtimes given different options (e.g. by turning language features on and off).

Console hosts are either provided by the browser vendors or, more likely, built from source. The jsvu CLI makes it easy to install and update the most common JavaScript engine binaries.

Host types are those provided by eshost, namely:

Shells:

Host Type	All Acceptable Values
ChakraCore	chakra, ch
Engine262	engine262
JavaScriptCore	javascriptcore, jsc
Nashorn	nashorn
Node	node
SpiderMonkey	jsshell, spidermonkey, sm
V8	d8, v8
XS	xs

Browsers:

Host Type	All Acceptable Values
chrome	chrome
edge	edge
firefox	firefox
safari	safari