What is the 'global' object in NodeJS
I\'ve just seen a weird behaviour of the this keyword in NodeJS environment. I\'m listing them with code. I\'ve run this codes with NodeJS v6.x, wi
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Very interesting:
var JSON = require('circular-json'); console.log('1) ' + JSON.stringify(this, null, 2)); (function(){ console.log('2) ' + JSON.stringify(this, null, 2)); }()); (function(){ 'use strict'; console.log('3) ' + JSON.stringify(this, null, 2)); }());will produce:
1) {} 2) { "global": "~", "process": { "title": "node", "version": "v6.9.1", "moduleLoadList": [ "Binding contextify", "Binding natives", "NativeModule events", "NativeModule util", "Binding uv", "NativeModule buffer", "Binding buffer", "Binding util", "NativeModule internal/util", "NativeModule timers", "Binding timer_wrap", "NativeModule internal/linkedlist", "NativeModule assert", "NativeModule internal/process", "Binding config", "NativeModule internal/process/warning", "NativeModule internal/process/next_tick", "NativeModule internal/process/promises", "NativeModule internal/process/stdio", "Binding constants", "NativeModule path", "NativeModule module", "NativeModule internal/module", "NativeModule vm", "NativeModule fs", "Binding fs", "NativeModule stream", "NativeModule _stream_readable", "NativeModule internal/streams/BufferList", "NativeModule _stream_writable", "NativeModule _stream_duplex", "NativeModule _stream_transform", "NativeModule _stream_passthrough", "Binding fs_event_wrap", "NativeModule console", "Binding tty_wrap", "NativeModule tty", "NativeModule net", "NativeModule internal/net", "Binding cares_wrap", "Binding tcp_wrap", "Binding pipe_wrap", "Binding stream_wrap", "Binding signal_wrap" ], "versions": { "http_parser": "2.7.0", "node": "6.9.1", "v8": "5.1.281.84", "uv": "1.9.1", "zlib": "1.2.8", "ares": "1.10.1-DEV", "icu": "57.1", "modules": "48", "openssl": "1.0.2j" }, "arch": "x64", "platform": "linux", "release": { "name": "node", "lts": "Boron", "sourceUrl": "https://nodejs.org/download/release/v6.9.1/node-v6.9.1.tar.gz", "headersUrl": "https://nodejs.org/download/release/v6.9.1/node-v6.9.1-headers.tar.gz" }, "argv": [ "/usr/local/bin/node", "/home/froth/freelancer-projects/thistest.js" ], "execArgv": [], "env": { "NVM_DIR": "/home/froth/.nvm", "LD_LIBRARY_PATH": "/opt/opencascade/lib", "CSF_UnitsDefinition": "/opt/opencascade/src/UnitsAPI/Units.dat", "CSF_GraphicShr": "/opt/opencascade/lib/libTKOpenGl.so", "CSF_EXCEPTION_PROMPT": "1", "LANG": "de_DE.UTF-8", "PROFILEHOME": "", "DISPLAY": ":0", "SHELL_SESSION_ID": "09b6f0f3b1d94c5f8aba3f8022075677", "NODE_PATH": "/usr/lib/node_modules", "COLORTERM": "truecolor", "NVM_CD_FLAGS": "", "MOZ_PLUGIN_PATH": "/usr/lib/mozilla/plugins", "CSF_IGESDefaults": "/opt/opencascade/src/XSTEPResource", "CSF_XCAFDefaults": "/opt/opencascade/src/StdResource", "XDG_VTNR": "1", "PAM_KWALLET5_LOGIN": "/tmp/kwallet5_froth.socket", "CSF_STEPDefaults": "/opt/opencascade/src/XSTEPResource", "XDG_SESSION_ID": "c2", "CSF_XSMessage": "/opt/opencascade/src/XSMessage", "USER": "froth", "DESKTOP_SESSION": "/usr/share/xsessions/awesome", "GTK2_RC_FILES": "/home/froth/.gtkrc-2.0", "PWD": "/home/froth/freelancer-projects", "HOME": "/home/froth", "XDG_SESSION_TYPE": "x11", "CSF_PluginDefaults": "/opt/opencascade/src/StdResource", "XDG_DATA_DIRS": "/usr/local/share/:/usr/share/:/var/lib/snapd/desktop", "NVM_IOJS_ORG_MIRROR": "https://iojs.org/dist", "KONSOLE_DBUS_SESSION": "/Sessions/1", "XDG_SESSION_DESKTOP": "", "CSF_StandardDefaults": "/opt/opencascade/src/StdResource", "CSF_StandardLiteDefaults": "/opt/opencascade/src/StdResource", "MMGT_CLEAR": "1", "KONSOLE_DBUS_WINDOW": "/Windows/1", "CSF_UnitsLexicon": "/opt/opencascade/src/UnitsAPI/Lexi_Expr.dat", "GTK_MODULES": "canberra-gtk-module", "MAIL": "/var/spool/mail/froth", "NVM_RC_VERSION": "", "CSF_XmlOcafResource": "/opt/opencascade/src/XmlOcafResource", "TERM": "xterm-256color", "SHELL": "/bin/bash", "KONSOLE_DBUS_SERVICE": ":1.23", "XDG_SESSION_CLASS": "user", "XDG_SEAT_PATH": "/org/freedesktop/DisplayManager/Seat0", "XDG_CURRENT_DESKTOP": "", "QT_LINUX_ACCESSIBILITY_ALWAYS_ON": "1", "KONSOLE_PROFILE_NAME": "Shell", "CASROOT": "/opt/opencascade", "NVM_NODEJS_ORG_MIRROR": "https://nodejs.org/dist", "COLORFGBG": "15;0", "XDG_SEAT": "seat0", "SHLVL": "2", "LANGUAGE": "", "WINDOWID": "29360134", "LOGNAME": "froth", "DBUS_SESSION_BUS_ADDRESS": "unix:path=/run/user/1000/bus", "XDG_RUNTIME_DIR": "/run/user/1000", "CSF_MDTVTexturesDirectory": "/opt/opencascade/src/Textures", "XAUTHORITY": "/home/froth/.Xauthority", "XDG_SESSION_PATH": "/org/freedesktop/DisplayManager/Session1", "PATH": "/home/froth/.gem/ruby/2.3.0/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/snap/bin:/usr/lib/jvm/default/bin:/opt/opencascade/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl", "CSF_LANGUAGE": "us", "CSF_SHMessage": "/opt/opencascade/src/SHMessage", "OLDPWD": "/home/froth", "_": "/usr/local/bin/node" }, "pid": 4658, "features": { "debug": false, "uv": true, "ipv6": true, "tls_npn": true, "tls_alpn": true, "tls_sni": true, "tls_ocsp": true, "tls": true }, "_needImmediateCallback": false, "execPath": "/usr/local/bin/node", "debugPort": 5858, "_events": { "SIGWINCH": [ null, null ] }, "_eventsCount": 4, "domain": null, "_exiting": false, "config": { "target_defaults": { "cflags": [], "default_configuration": "Release", "defines": [], "include_dirs": [], "libraries": [] }, "variables": { "asan": 0, "debug_devtools": "node", "force_dynamic_crt": 0, "gas_version": "2.23", "host_arch": "x64", "icu_data_file": "icudt57l.dat", "icu_data_in": "../../deps/icu-small/source/data/in/icudt57l.dat", "icu_endianness": "l", "icu_gyp_path": "tools/icu/icu-generic.gyp", "icu_locales": "en,root", "icu_path": "deps/icu-small", "icu_small": true, "icu_ver_major": "57", "node_byteorder": "little", "node_enable_d8": false, "node_enable_v8_vtunejit": false, "node_install_npm": true, "node_module_version": 48, "node_no_browser_globals": false, "node_prefix": "/", "node_release_urlbase": "https://nodejs.org/download/release/", "node_shared": false, "node_shared_cares": false, "node_shared_http_parser": false, "node_shared_libuv": false, "node_shared_openssl": false, "node_shared_zlib": false, "node_tag": "", "node_use_bundled_v8": true, "node_use_dtrace": false, "node_use_etw": false, "node_use_lttng": false, "node_use_openssl": true, "node_use_perfctr": false, "node_use_v8_platform": true, "openssl_fips": "", "openssl_no_asm": 0, "shlib_suffix": "so.48", "target_arch": "x64", "uv_parent_path": "/deps/uv/", "uv_use_dtrace": false, "v8_enable_gdbjit": 0, "v8_enable_i18n_support": 1, "v8_inspector": true, "v8_no_strict_aliasing": 1, "v8_optimized_debug": 0, "v8_random_seed": 0, "v8_use_snapshot": true, "want_separate_host_toolset": 0 } }, "stdout": { "connecting": false, "_hadError": false, "_handle": { "bytesRead": 0, "_externalStream": {}, "fd": 9, "writeQueueSize": 0, "owner": "~process~stdout" }, "_parent": null, "_host": null, "_readableState": { "objectMode": false, "highWaterMark": 16384, "buffer": { "head": null, "tail": null, "length": 0 }, "length": 0, "pipes": null, "pipesCount": 0, "flowing": null, "ended": false, "endEmitted": false, "reading": false, "sync": true, "needReadable": false, "emittedReadable": false, "readableListening": false, "resumeScheduled": false, "defaultEncoding": "utf8", "ranOut": false, "awaitDrain": 0, "readingMore": false, "decoder": null, "encoding": null }, "readable": false, "domain": null, "_events": {}, "_eventsCount": 3, "_writableState": { "objectMode": false, "highWaterMark": 16384, "needDrain": false, "ending": false, "ended": false, "finished": false, "decodeStrings": false, "defaultEncoding": "utf8", "length": 0, "writing": false, "corked": 0, "sync": false, "bufferProcessing": false, "writecb": null, "writelen": 0, "bufferedRequest": null, "lastBufferedRequest": null, "pendingcb": 1, "prefinished": false, "errorEmitted": false, "bufferedRequestCount": 0, "corkedRequestsFree": { "next": null, "entry": null } }, "writable": true, "allowHalfOpen": false, "destroyed": false, "_bytesDispatched": 6, "_sockname": null, "_writev": null, "_pendingData": null, "_pendingEncoding": "", "server": null, "_server": null, "columns": 84, "rows": 84, "_type": "tty", "fd": 1, "_isStdio": true }, "stderr": { "connecting": false, "_hadError": false, "_handle": { "bytesRead": 0, "_externalStream": {}, "fd": 11, "writeQueueSize": 0, "owner": "~process~stderr" }, "_parent": null, "_host": null, "_readableState": { "objectMode": false, "highWaterMark": 16384, "buffer": { "head": null, "tail": null, "length": 0 }, "length": 0, "pipes": null, "pipesCount": 0, "flowing": null, "ended": false, "endEmitted": false, "reading": false, "sync": true, "needReadable": false, "emittedReadable": false, "readableListening": false, "resumeScheduled": false, "defaultEncoding": "utf8", "ranOut": false, "awaitDrain": 0, "readingMore": false, "decoder": null, "encoding": null }, "readable": false, "domain": null, "_events": {}, "_eventsCount": 3, "_writableState": { "objectMode": false, "highWaterMark": 16384, "needDrain": false, "ending": false, "ended": false, "finished": false, "decodeStrings": false, "defaultEncoding": "utf8", "length": 0, "writing": false, "corked": 0, "sync": true, "bufferProcessing": false, "writecb": null, "writelen": 0, "bufferedRequest": null, "lastBufferedRequest": null, "pendingcb": 0, "prefinished": false, "errorEmitted": false, "bufferedRequestCount": 0, "corkedRequestsFree": { "next": null, "entry": null } }, "writable": true, "allowHalfOpen": false, "destroyed": false, "_bytesDispatched": 0, "_sockname": null, "_writev": null, "_pendingData": null, "_pendingEncoding": "", "server": null, "_server": null, "columns": 84, "rows": 84, "_type": "tty", "fd": 2, "_isStdio": true }, "stdin": { "connecting": false, "_hadError": false, "_handle": { "bytesRead": 0, "_externalStream": {}, "fd": 12, "writeQueueSize": 0, "owner": "~process~stdin", "reading": false }, "_parent": null, "_host": null, "_readableState": { "objectMode": false, "highWaterMark": 0, "buffer": { "head": null, "tail": null, "length": 0 }, "length": 0, "pipes": null, "pipesCount": 0, "flowing": null, "ended": false, "endEmitted": false, "reading": false, "sync": false, "needReadable": true, "emittedReadable": false, "readableListening": false, "resumeScheduled": false, "defaultEncoding": "utf8", "ranOut": false, "awaitDrain": 0, "readingMore": false, "decoder": null, "encoding": null }, "readable": true, "domain": null, "_events": {}, "_eventsCount": 4, "_writableState": { "objectMode": false, "highWaterMark": 0, "needDrain": false, "ending": false, "ended": false, "finished": false, "decodeStrings": false, "defaultEncoding": "utf8", "length": 0, "writing": false, "corked": 0, "sync": true, "bufferProcessing": false, "writecb": null, "writelen": 0, "bufferedRequest": null, "lastBufferedRequest": null, "pendingcb": 0, "prefinished": false, "errorEmitted": false, "bufferedRequestCount": 0, "corkedRequestsFree": { "next": null, "entry": null } }, "writable": false, "allowHalfOpen": false, "destroyed": false, "_bytesDispatched": 0, "_sockname": null, "_writev": null, "_pendingData": null, "_pendingEncoding": "", "server": null, "_server": null, "isRaw": false, "isTTY": true, "fd": 0 }, "argv0": "node", "mainModule": { "id": ".", "exports": {}, "parent": null, "filename": "/home/froth/freelancer-projects/thistest.js", "loaded": false, "children": [ { "id": "/home/froth/freelancer-projects/node_modules/circular-json/build/circular-json.node.js", "exports": {}, "parent": "~process~mainModule", "filename": "/home/froth/freelancer-projects/node_modules/circular-json/build/circular-json.node.js", "loaded": true, "children": [], "paths": [ "/home/froth/freelancer-projects/node_modules/circular-json/build/node_modules", "/home/froth/freelancer-projects/node_modules/circular-json/node_modules", "/home/froth/freelancer-projects/node_modules", "/home/froth/node_modules", "/home/node_modules", "/node_modules" ] } ], "paths": [ "/home/froth/freelancer-projects/node_modules", "/home/froth/node_modules", "/home/node_modules", "/node_modules" ] } }, "console": {} } 3) undefinedIn
3)this is undefined as it is not autoboxed to an object in strict mode. That means that there is no root object in this context. If you do not use strict mode then your code is boxed by a parent scope.As you can see in the output, within nodejs there is lot of information about node internal stuff.In
1)the output is an empty object because in the top-level code in a node module, this is the equivalent to module.exports and module.exports is empty in this example.
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