I was working on node and want to see the compiled bytecode . Is there a way we can compile a js file and save the bytecode in a seperate file using node ??
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1javascript isn't compiled (in the traditional sense) - it's an interpreted languageJaromanda X– Jaromanda X2017-04-18 01:11:38 +00:00Commented Apr 18, 2017 at 1:11
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Yeah, I mean interpreted/compiled into bytecode by node. Node do compile JS into bytecode. I did not get your comment.user2225263– user22252632017-04-18 01:12:58 +00:00Commented Apr 18, 2017 at 1:12
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2The basic answer is "no".Pointy– Pointy2017-04-18 01:14:55 +00:00Commented Apr 18, 2017 at 1:14
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1Node (or rather V8 JS engine that Node runs on) does not compile into bytecode, it is compiled on-the-fly into native code. If you wish to see the generated native code, this answer might be of use.Amadan– Amadan2017-04-18 01:25:16 +00:00Commented Apr 18, 2017 at 1:25
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1Note that other JS engines do have bytecode; e.g. SpiderMonkey, used by Mozilla, does have bytecode; and Rhino compiles JavaScript to JVM. None of those are used by Node, though.Amadan– Amadan2017-04-18 01:57:00 +00:00Commented Apr 18, 2017 at 1:57
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2 Answers
You can use --trace_ignition to get the intermediary byte code:
#node --trace_ignition a.js
-> 0x3aa1c02bf66e @ 0 : 80 StackCheck
-> 0x3aa1c02bf66f @ 1 : 13 13 LdaImmutableCurrentContextSlot [19]
[ accumulator <- 0xd88d0f93ce9 <JS Function NativeModule (SharedFunctionInfo 0x3aa1c02b86a1)> ]
-> 0x3aa1c02bf671 @ 3 : 1f f7 Star r3
[ accumulator -> 0xd88d0f93ce9 <JS Function NativeModule (SharedFunctionInfo 0x3aa1c02b86a1)> ]
[ r3 <- 0xd88d0f93ce9 <JS Function NativeModule (SharedFunctionInfo 0x3aa1c02b86a1)> ]
-> 0x3aa1c02bf673 @ 5 : 21 f7 00 04 LdaNamedProperty r3, [0], [4]
[ r3 -> 0xd88d0f93ce9 <JS Function NativeModule (SharedFunctionInfo 0x3aa1c02b86a1)> ]
[ accumulator <- 0x3aa1c02bcb49 <JS Function NativeModule.getSource (SharedFunctionInfo 0x3aa1c02b8c51)> ]
-> 0x3aa1c02bf677 @ 9 : 1f f8 Star r2
[ accumulator -> 0x3aa1c02bcb49 <JS Function NativeModule.getSource (SharedFunctionInfo 0x3aa1c02b8c51)> ]
[ r2 <- 0x3aa1c02bcb49 <JS Function NativeModule.getSource (SharedFunctionInfo 0x3aa1c02b8c51)> ]
-> 0x3aa1c02bf679 @ 11 : 21 02 01 06 LdaNamedProperty <this>, [1], [6]
[ <this> -> 0xd88d0f9a329 <a NativeModule with map 0x11929f412849> ]
[ accumulator <- 0x3aa1c02bb969 <String[6]: events> ]
-> 0x3aa1c02bf67d @ 15 : 1f f6 Star r4
[ accumulator -> 0x3aa1c02bb969 <String[6]: events> ]
[ r4 <- 0x3aa1c02bb969 <String[6]: events> ]
-> 0x3aa1c02bf67f @ 17 : 45 f8 f7 02 02 CallProperty r2, r3-r4, [2]
[ r2 -> 0x3aa1c02bcb49 <JS Function NativeModule.getSource (SharedFunctionInfo 0x3aa1c02b8c51)> ]
[ r3 -> 0xd88d0f93ce9 <JS Function NativeModule (SharedFunctionInfo 0x3aa1c02b86a1)> ]
[ r4 -> 0x3aa1c02bb969 <String[6]: events> ]
[ accumulator <- 0xd88d0f956f1 <Very long string[15201]> ]
-> 0x3aa1c02bf684 @ 22 : 1f f9 Star r1
[ accumulator -> 0xd88d0f956f1 <Very long string[15201]> ]
[ r1 <- 0xd88d0f956f1 <Very long string[15201]> ]
You can use --print_code to get the natively generated code:
#node --print_code -e 'console.log("hello")' > code.txt
#head -100 code.txt
--- Raw source ---
(){
var originAssert = this.assert;
originAssert.apply = Function.prototype.apply;
this.assert = assertWrapper;
assertWrapper.toString = () => originAssert.toString();
function assertWrapper(){
if (!!arguments[0]) return;
originAssert.apply(null, arguments);
}
})
--- Code ---
source_position = 9
kind = FUNCTION
compiler = full-codegen
Instructions (size = 500)
0x29b8195043c0 0 55 push rbp
0x29b8195043c1 1 4889e5 REX.W movq rbp,rsp
0x29b8195043c4 4 56 push rsi
0x29b8195043c5 5 57 push rdi
0x29b8195043c6 6 488b4f2f REX.W movq rcx,[rdi+0x2f]
0x29b8195043ca 10 488b4907 REX.W movq rcx,[rcx+0x7]
0x29b8195043ce 14 83411b01 addl [rcx+0x1b],0x1
0x29b8195043d2 18 41ff75a0 push [r13-0x60]
0x29b8195043d6 22 b801000000 movl rax,0x1
0x29b8195043db 27 e80038f3ff call FastNewFunctionContextFunction (0x29b819437be0) ;; code: BUILTIN
0x29b8195043e0 32 488bf0 REX.W movq rsi,rax
0x29b8195043e3 35 488945f8 REX.W movq [rbp-0x8],rax
Hope this helps.
Comments
You can see the byte code
If you want to see V8's bytecode of JavaScript code, you can print it by calling D8 or Node.js (8.3 or higher) with the flag --print-bytecode. For Chrome, start Chrome from the command line with --js-flags="--print-bytecode", see Run Chromium with flags.
Read full article here Understanding V8 Byte code
Not sure how to print into a file.
1 Comment
greg
You can redirect the output to a file using output redirection via
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