Identyfikatory JavaScript nie używać

Question

Właśnie odkryłem, że nazywanie zmiennej arguments jest złym pomysłem.

var arguments = 5; 

(function() { 
    console.log(arguments); 
})(); 

Output: []

Okazuje się, że arguments jest "a local variable available within all functions" więc w każdym nowym kontekście realizacji, arguments jest zasłonięta.

Moje pytanie brzmi: czy istnieją inne takie zdradzieckie nazwy, które, tak jak arguments, nie są prawdziwe reserved words, ale czy będą nadal powodować problemy?

Answer 1

Nie ma żadnych innych automatycznych symbole wewnątrz funkcji (oprócz this, ale nie można utworzyć zmienną o tej nazwie i tak), jeśli to masz na myśli. Ale istnieje kilka domyślnych zmiennych globalnych, więc zdefiniowanie zmiennej o tej samej nazwie wewnątrz funkcji spowoduje przesłonięcie zmiennej globalnej.

Answer 2

Tak. Na przykład: window lub document. Zobacz dłuższą listę here ("inne słowa kluczowe javascript").

Nie zaleca się używania żadnego z nich, nawet jeśli niektóre będą działać zgodnie z przeznaczeniem.

Edytuj: Jak wspomniano w javascript.about.com, "Mimo że nie są słowami zastrzeżonymi, należy unikać używania tych słów jako zmiennych i funkcji.". Zawierają one głównie te same rzeczy, które zostały sklasyfikowane jako predefined classes and objects i .

Przykład problemu:

var window = 5; 

(function() { 
    alert(window); 
})(); 

powyższy kod ma nieprzewidywalne wyniki ze względu na fakt, że window to słowo odnosi się do obiektu window. Firefox zapobiega modyfikacjom, więc alarm będzie nadal odnosił się do obiektu okna, podczas gdy w IE8 dostaniesz alert o wartości 5.

Answer 3

można uzyskać listę wszystkich nazw stosowanych w globalnej przestrzeni nazw, wykonując to w konsoli:

var t = []; 
for(v in this){t.push(v)} 
console.log(t.sort()); 

Wynik:

["$","ArrayBuffer","Attr","Audio","AudioProcessingEvent","BeforeLoadEvent","Blob","CDATASection","CSSCharsetRule","CSSFontFaceRule","CSSImportRule","CSSMediaRule","CSSPageRule","CSSPrimitiveValue","CSSRule","CSSRuleList","CSSStyleDeclaration","CSSStyleRule","CSSStyleSheet","CSSValue","CSSValueList","CTIsPlayback","CanvasGradient","CanvasPattern","CanvasRenderingContext2D","CharacterData","ClientRect","ClientRectList","Clipboard","CloseEvent","Comment","CompositionEvent","Counter","CustomEvent","DOMException","DOMImplementation","DOMParser","DOMSettableTokenList","DOMStringList","DOMStringMap","DOMTokenList","DataView","DeviceOrientationEvent","Document","DocumentFragment","DocumentType","Element","Entity","EntityReference","ErrorEvent","Event","EventEmitter","EventException","EventSource","File","FileError","FileList","FileReader","Float32Array","Float64Array","FormData","Generator","HTMLAllCollection","HTMLAnchorElement","HTMLAppletElement","HTMLAreaElement","HTMLAudioElement","HTMLBRElement","HTMLBaseElement","HTMLBaseFontElement","HTMLBodyElement","HTMLButtonElement","HTMLCanvasElement","HTMLCollection","HTMLDListElement","HTMLDataListElement","HTMLDirectoryElement","HTMLDivElement","HTMLDocument","HTMLElement","HTMLEmbedElement","HTMLFieldSetElement","HTMLFontElement","HTMLFormElement","HTMLFrameElement","HTMLFrameSetElement","HTMLHRElement","HTMLHeadElement","HTMLHeadingElement","HTMLHtmlElement","HTMLIFrameElement","HTMLImageElement","HTMLInputElement","HTMLKeygenElement","HTMLLIElement","HTMLLabelElement","HTMLLegendElement","HTMLLinkElement","HTMLMapElement","HTMLMarqueeElement","HTMLMediaElement","HTMLMenuElement","HTMLMetaElement","HTMLMeterElement","HTMLModElement","HTMLOListElement","HTMLObjectElement","HTMLOptGroupElement","HTMLOptionElement","HTMLOutputElement","HTMLParagraphElement","HTMLParamElement","HTMLPreElement","HTMLProgressElement","HTMLQuoteElement","HTMLScriptElement","HTMLSelectElement","HTMLSourceElement","HTMLSpanElement","HTMLStyleElement","HTMLTableCaptionElement","HTMLTableCellElement","HTMLTableColElement","HTMLTableElement","HTMLTableRowElement","HTMLTableSectionElement","HTMLTextAreaElement","HTMLTitleElement","HTMLTrackElement","HTMLUListElement","HTMLUnknownElement","HTMLVideoElement","HashChangeEvent","IceCandidate","Image","ImageData","Int16Array","Int32Array","Int8Array","KeyboardEvent","Markdown","MediaController","MediaError","MediaList","MediaStreamEvent","MessageChannel","MessageEvent","MessagePort","MimeType","MimeTypeArray","MouseEvent","MutationEvent","NamedNodeMap","Node","NodeFilter","NodeList","Notation","Notification","OfflineAudioCompletionEvent","Option","OverflowEvent","PERSISTENT","PR","PR_SHOULD_USE_CONTINUATION","PageTransitionEvent","Plugin","PluginArray","PopStateEvent","ProcessingInstruction","ProgressEvent","RGBColor","RTCIceCandidate","RTCSessionDescription","Range","RangeException","Rect","SQLException","SVGAElement","SVGAltGlyphDefElement","SVGAltGlyphElement","SVGAltGlyphItemElement","SVGAngle","SVGAnimateColorElement","SVGAnimateElement","SVGAnimateMotionElement","SVGAnimateTransformElement","SVGAnimatedAngle","SVGAnimatedBoolean","SVGAnimatedEnumeration","SVGAnimatedInteger","SVGAnimatedLength","SVGAnimatedLengthList","SVGAnimatedNumber","SVGAnimatedNumberList","SVGAnimatedPreserveAspectRatio","SVGAnimatedRect","SVGAnimatedString","SVGAnimatedTransformList","SVGCircleElement","SVGClipPathElement","SVGColor","SVGComponentTransferFunctionElement","SVGCursorElement","SVGDefsElement","SVGDescElement","SVGDocument","SVGElement","SVGElementInstance","SVGElementInstanceList","SVGEllipseElement","SVGException","SVGFEBlendElement","SVGFEColorMatrixElement","SVGFEComponentTransferElement","SVGFECompositeElement","SVGFEConvolveMatrixElement","SVGFEDiffuseLightingElement","SVGFEDisplacementMapElement","SVGFEDistantLightElement","SVGFEDropShadowElement","SVGFEFloodElement","SVGFEFuncAElement","SVGFEFuncBElement","SVGFEFuncGElement","SVGFEFuncRElement","SVGFEGaussianBlurElement","SVGFEImageElement","SVGFEMergeElement","SVGFEMergeNodeElement","SVGFEMorphologyElement","SVGFEOffsetElement","SVGFEPointLightElement","SVGFESpecularLightingElement","SVGFESpotLightElement","SVGFETileElement","SVGFETurbulenceElement","SVGFilterElement","SVGFontElement","SVGFontFaceElement","SVGFontFaceFormatElement","SVGFontFaceNameElement","SVGFontFaceSrcElement","SVGFontFaceUriElement","SVGForeignObjectElement","SVGGElement","SVGGlyphElement","SVGGlyphRefElement","SVGGradientElement","SVGHKernElement","SVGImageElement","SVGLength","SVGLengthList","SVGLineElement","SVGLinearGradientElement","SVGMPathElement","SVGMarkerElement","SVGMaskElement","SVGMatrix","SVGMetadataElement","SVGMissingGlyphElement","SVGNumber","SVGNumberList","SVGPaint","SVGPathElement","SVGPathSeg","SVGPathSegArcAbs","SVGPathSegArcRel","SVGPathSegClosePath","SVGPathSegCurvetoCubicAbs","SVGPathSegCurvetoCubicRel","SVGPathSegCurvetoCubicSmoothAbs","SVGPathSegCurvetoCubicSmoothRel","SVGPathSegCurvetoQuadraticAbs","SVGPathSegCurvetoQuadraticRel","SVGPathSegCurvetoQuadraticSmoothAbs","SVGPathSegCurvetoQuadraticSmoothRel","SVGPathSegLinetoAbs","SVGPathSegLinetoHorizontalAbs","SVGPathSegLinetoHorizontalRel","SVGPathSegLinetoRel","SVGPathSegLinetoVerticalAbs","SVGPathSegLinetoVerticalRel","SVGPathSegList","SVGPathSegMovetoAbs","SVGPathSegMovetoRel","SVGPatternElement","SVGPoint","SVGPointList","SVGPolygonElement","SVGPolylineElement","SVGPreserveAspectRatio","SVGRadialGradientElement","SVGRect","SVGRectElement","SVGRenderingIntent","SVGSVGElement","SVGScriptElement","SVGSetElement","SVGStopElement","SVGStringList","SVGStyleElement","SVGSwitchElement","SVGSymbolElement","SVGTRefElement","SVGTSpanElement","SVGTextContentElement","SVGTextElement","SVGTextPathElement","SVGTextPositioningElement","SVGTitleElement","SVGTransform","SVGTransformList","SVGUnitTypes","SVGUseElement","SVGVKernElement","SVGViewElement","SVGViewSpec","SVGZoomAndPan","SVGZoomEvent","Selection","SessionDescription","SharedWorker","SpeechInputEvent","StackExchange","Storage","StorageEvent","StyleSheet","StyleSheetList","TEMPORARY","Text","TextEvent","TextMetrics","TextTrack","TextTrackCue","TextTrackCueList","TextTrackList","TimeRanges","TouchEvent","TrackEvent","UIEvent","URL","Uint16Array","Uint32Array","Uint8Array","Uint8ClampedArray","WebGLActiveInfo","WebGLBuffer","WebGLContextEvent","WebGLFramebuffer","WebGLProgram","WebGLRenderbuffer","WebGLRenderingContext","WebGLShader","WebGLShaderPrecisionFormat","WebGLTexture","WebGLUniformLocation","WebKitAnimationEvent","WebKitBlobBuilder","WebKitCSSFilterValue","WebKitCSSKeyframeRule","WebKitCSSKeyframesRule","WebKitCSSMatrix","WebKitCSSRegionRule","WebKitCSSTransformValue","WebKitIntent","WebKitMediaSource","WebKitMutationObserver","WebKitPoint","WebKitSourceBuffer","WebKitSourceBufferList","WebKitTransitionEvent","WebSocket","WheelEvent","Window","WinterBash","Worker","XMLDocument","XMLHttpRequest","XMLHttpRequestException","XMLHttpRequestProgressEvent","XMLHttpRequestUpload","XMLSerializer","XPathEvaluator","XPathException","XPathResult","XSLTProcessor","__qc","_gaq","_gat","_qevents","addEventListener","alert","apiCallbacks","applicationCache","atob","blur","btoa","captureEvents","careers_adselector","careers_adurl","careers_companycssurl","careers_cssurl","careers_leaderboardcssurl","chrome","clearInterval","clearTimeout","clientInformation","close","closed","confirm","console","crypto","defaultStatus","defaultstatus","devicePixelRatio","dispatchEvent","document","event","external","find","focus","frameElement","frames","gaGlobal","gauth","genuwine","getComputedStyle","getMatchedCSSRules","getSelection","history","i","initFadingHelpText","initTagRenderer","innerHeight","innerWidth","jQuery","jQuery171005593172716908157_1357215797040","jQuery171005593172716908157_1357215797041","length","localStorage","location","locationbar","matchMedia","menubar","moveBy","moveScroller","moveTo","name","navigator","offscreenBuffering","onabort","onbeforeunload","onblur","oncanplay","oncanplaythrough","onchange","onclick","oncontextmenu","ondblclick","ondeviceorientation","ondrag","ondragend","ondragenter","ondragleave","ondragover","ondragstart","ondrop","ondurationchange","onemptied","onended","onerror","onfocus","onhashchange","oninput","oninvalid","onkeydown","onkeypress","onkeyup","onload","onloadeddata","onloadedmetadata","onloadstart","onmessage","onmousedown","onmousemove","onmouseout","onmouseover","onmouseup","onmousewheel","onoffline","ononline","onpagehide","onpageshow","onpause","onplay","onplaying","onpopstate","onprogress","onratechange","onreset","onresize","onscroll","onsearch","onseeked","onseeking","onselect","onstalled","onstorage","onsubmit","onsuspend","ontimeupdate","onunload","onvolumechange","onwaiting","onwebkitanimationend","onwebkitanimationiteration","onwebkitanimationstart","onwebkittransitionend","open","openDatabase","opener","outerHeight","outerWidth","pageXOffset","pageYOffset","parent","performance","personalbar","postMessage","prepareEditor","prettyPrint","prettyPrintOne","print","profileLink","prompt","quantserve","releaseEvents","removeEventListener","resizeBy","resizeTo","sanitizeAndSplitTags","screen","screenLeft","screenTop","screenX","screenY","scriptSrc","scroll","scrollBy","scrollTo","scrollX","scrollY","scrollbars","self","sessionStorage","setInterval","setTimeout","showFadingHelpText","showModalDialog","status","statusbar","stop","styleCode","styleMedia","t","tagRenderer","tagRendererRaw","toolbar","top","uh","v","v8Intl","votesCast","webkitAudioContext","webkitAudioPannerNode","webkitCancelAnimationFrame","webkitCancelRequestAnimationFrame","webkitConvertPointFromNodeToPage","webkitConvertPointFromPageToNode","webkitIDBCursor","webkitIDBDatabase","webkitIDBDatabaseException","webkitIDBFactory","webkitIDBIndex","webkitIDBKeyRange","webkitIDBObjectStore","webkitIDBRequest","webkitIDBTransaction","webkitIndexedDB","webkitIntent","webkitMediaStream","webkitNotifications","webkitPostMessage","webkitRTCPeerConnection","webkitRequestAnimationFrame","webkitRequestFileSystem","webkitResolveLocalFileSystemURL","webkitStorageInfo","webkitURL","window"]; 

Tak, to nie mogę/powinnam” być używane (przynajmniej w Google Chrome) w zakresie globalnym. Jeśli zadeklarujesz je jako zmienne w zakresie lokalnym, wszystko będzie dobrze.
Nie będzie to zawierało nazw all, ponieważ arguments jest dostępne tylko w zakresie funkcji, na przykład.

_{Uwaga: ta funkcja nie zwróci wszystkie zmienne globalne z bibliotek, również}