Video: Puas yog cov chav kawm hoisted hauv JavaScript?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Ntau yam zoo li lawv cov haujlwm ua haujlwm, chav kawm JavaScript tshaj tawm yog nqa . Txawm li cas los xij, lawv nyob twj ywm uninitialized kom txog thaum kev ntsuam xyuas. Qhov no txhais tau hais tias koj yuav tsum tshaj tawm a chav kawm ua ntej koj yuav siv tau.
Tsis tas li ntawd, chav kawm JavaScript yog dab tsi?
Cov chav kawm hauv JavaScript yog ib tug tshwj xeeb syntax rau nws prototypical qub txeeg qub teg qauv uas yog ib tug piv txwv nyob rau hauv chav kawm -raws li hom lus taw qhia. Cov chav kawm tsuas yog cov haujlwm tshwj xeeb ntxiv rau ES6 uas yog txhais tau tias yuav ua raws li chav kawm lo lus tseem ceeb los ntawm lwm yam lus no.
Ib yam li ntawd, hoisting hauv JavaScript nrog piv txwv yog dab tsi? Hoisting yog cov JavaScript tus neeg txhais lus qhov kev txiav txim ntawm kev txav txhua qhov sib txawv thiab cov lus tshaj tawm ua haujlwm mus rau sab saum toj ntawm qhov tam sim no. (function() { var foo; var bar; var baz; foo = 1; alert(foo + "" + bar + " " + baz); bar = 2; baz = 3; })(); Tam sim no nws ua rau kev nkag siab vim li cas qhov thib ob piv txwv tsis tau tsim ib qho kev zam.
Ntawm no, cov lus hais hauv chav kawm hoisted?
Hoisting Class Expressions Ib yam li muaj nuj nqi cov lus qhia , cov lus qhia hauv chav kawm kuj tsis yog nqa.
Puas yog cia thiab Const hoisted?
Yog li, los teb koj cov lus nug, yog, cia thiab const hoist tab sis koj tsis tuaj yeem nkag mus rau lawv ua ntej qhov kev tshaj tawm tiag tiag raug ntsuas ntawm lub sijhawm ua haujlwm. ES6 qhia Cia variables uas tuaj nrog block theem scope. Thaum koj txhais qhov sib txawv nrog var lo lus tseem ceeb, nws paub tag nrho cov haujlwm txij li lub sijhawm nws tau txhais.
Pom zoo:
Dab tsi yog qhov txawv ntawm chav kawm sab hauv thiab cov chav nested?
Cov chav kawm uas tau tshaj tawm yam tsis siv qhov zoo li qub yog hu ua chav kawm sab hauv lossis chav kawm tsis zoo li qub. Cov chav kawm Staticnested yog chav kawm zoo li lwm cov tswv cuab zoo li qub ntawm cov chav kawm sab nrauv. Txawm li cas los xij, cov chav kawm sab hauv yog khi toinstance thiab nws tuaj yeem nkag mus rau cov tswv cuab ntawm pawg enclosingclass
Dab tsi yog ob chav kawm tshwj xeeb hauv hierarchy ntawm Java zam chav kawm?
Chav Kawm Exception muaj ob lub ntsiab subclasses: IOException class thiab RuntimeException Class. Hauv qab no yog cov npe ntawm feem ntau kuaj xyuas thiab tsis tau txheeb xyuas Java's Built-in Exceptions
Peb puas tuaj yeem muaj ntau chav kawm pej xeem hauv chav kawm hauv Java?
Yog, nws ua tau. Txawm li cas los xij, muaj peev xwm tsuas yog ib pawg pej xeem ib. java cov ntaub ntawv, raws li publicclasses yuav tsum muaj tib lub npe raws li cov ntaub ntawv qhov chaw. OneJava cov ntaub ntawv tuaj yeem muaj ntau chav kawm nrog kev txwv uas tsuas yog ib qho ntawm lawv tuaj yeem ua pej xeem
Kuv puas tuaj yeem ntxiv cov tub ntxhais kawm rau hauv Google chav kawm?
Thaum tso npe rau koj cov tub ntxhais kawm, muaj peb txoj kev xaiv uas koj muaj: Sau npe Code, ntxiv los ntawm email, lossis importvia Google Classroom. Txhawm rau tso npe cov tub ntxhais kawm, xaiv chav kawm uas koj xav ntxiv rau ntawm nplooj ntawv tseem ceeb ntawm koj lub dashboard, tom qab ntawd nyem rau ntawm 'Cov Tub Ntxhais Kawm' tab. Thaum kawg, nyem Ntxiv Cov Tub Kawm Ntawv
Chav kawm piav qhia txog tus qauv ntawm chav kawm yog dab tsi?
Nyob rau hauv object-oriented programming, ib chav kawm yog ib tug template txhais ntawm txoj kev s thiab txawv txawv s nyob rau hauv ib tug tej yam khoom. Yog li, ib yam khoom yog ib qho piv txwv tshwj xeeb ntawm chav kawm; nws muaj cov txiaj ntsig tiag tiag tsis yog hloov pauv. Cov qauv ntawm ib chav kawm thiab nws cov subclasses yog hu ua chav kawm hierarchy