Video: Dab tsi yog qhov tsis raug ntaus yuam kev hauv JavaScript?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Uncaught txhais tau tias yuam kev tsis tau ntes tau nyob rau hauv daim ntawv catch, thiab TypeError yog cov yuam kev npe. undefined tsis muaj nuj nqi: Qhov no yog cov lus ntu. Nrog yuam kev cov lus, koj yuav tsum tau nyeem lawv cov lus. Piv txwv li nyob rau hauv cov ntaub ntawv no nws txhais tau hais tias cov code sim siv undefined zoo li nws yog ib tug muaj nuj nqi.
Hauv qhov no, hom kev ua yuam kev hauv JS yog dab tsi?
Tib yam mus rau hauv JavaScript ! Yog tias koj ntxiv 1 thiab H hauv JavaScript lossis thaum koj sim ua haujlwm ntawm ob qhov kev ua haujlwm tsis sib xws hom , JavaScript pov a TypeError . Rau MDN: 'A TypeError raug pov tseg thaum ib qho kev ua haujlwm lossis kev sib cav dhau mus rau qhov ua haujlwm tsis sib haum nrog hom xav tau los ntawm tus neeg teb xov tooj lossis kev ua haujlwm.
Tsis tas li ntawd, Cannot read property of undefined txhais li cas? Uncaught TypeError: Nyeem tsis tau cov cuab yeej 'tsis' ntawm tsis tau txhais . Hauv cov ntsiab lus tseem ceeb, undefined txhais tau tias tias qhov sib txawv tau tshaj tawm tab sis tseem tsis tau muab tus nqi.
Ib yam li ntawd, tib neeg nug, tsis yog kev ua haujlwm hauv JS?
Qhov tseeb, koj muaj a muaj nuj nqi pointer hauv EAX, txij li thaum lub JS cav tsis tuaj yeem qhia tias qhov sib txawv ntawm lub sijhawm sib sau - nws tsuas tuaj yeem paub thaum lub sijhawm khiav. Nws txhais tau tias, lus, nws tsis yog ib txoj haujlwm ! Qhov ntawd txhais tau tias koj tab tom ua ib yam dab tsi (abbreviated) zoo li no: muaj nuj nqi foo(){
Hom kev ua yuam kev yog dab tsi?
Nyob rau hauv statistical hypothesis test, a hom Kuv yuam kev yog qhov tsis lees paub qhov tseeb null hypothesis (tseem hu ua "false positive" nrhiav lossis xaus), thaum hom II yuam kev yog qhov tsis lees paub ntawm qhov tsis tseeb qhov kev xav tsis tseeb (tseem hu ua "false negative" nrhiav lossis xaus).
Pom zoo:
Dab tsi yog qhov sib txawv loj ntawm kev txheeb xyuas qhov yuam kev thiab kev kho cov lej yuam kev?
Ob qhov kev tshawb nrhiav qhov yuam kev thiab kev kho qhov yuam kev yuav tsum muaj qee qhov ntawm cov ntaub ntawv rov qab xa mus nrog cov ntaub ntawv tiag tiag; kev kho yuav tsum muaj ntau tshaj li kev tshawb nrhiav. Parity bits yog ib txoj hauv kev yooj yim rau kev tshawb nrhiav qhov yuam kev. Ib qho parity me ntsis yog ib qho ntxiv me ntsis xa nrog cov ntaub ntawv uas tsuas yog 1-ntsis suav ntawm cov ntaub ntawv
Puas yog Java tsis muaj zog ntaus lossis ntaus ntaus?
Java yog hom lus statically-typed. Hauv hom lus uas tsis muaj zog, cov kev hloov pauv tuaj yeem raug yuam rau cov hom tsis sib xws, thaum hauv hom lus uas lawv tsis tuaj yeem ua tsis tau, thiab yuav tsum tau hloov dua siab tshiab. Ob qho tib si Java thiab Python yog hom lus zoo heev. Piv txwv ntawm cov lus tsis muaj zog yog Perl thiab Rexx
Dab tsi yog qhov txawv ntawm kev sib raug zoo unary kev sib raug zoo binary thiab kev sib raug zoo ternary?
Kev sib raug zoo tsis sib xws yog thaum ob tus neeg koom hauv kev sib raug zoo yog tib lub koom haum. Piv txwv li: Cov ncauj lus yuav yog qhov yuav tsum tau ua ua ntej rau lwm yam kev kawm. Kev sib raug zoo ternary yog thaum peb lub koom haum koom nrog kev sib raug zoo
Dab tsi yog qhov txawv ntawm kev sib raug zoo thiab tsis muaj kev sib raug zoo databases?
Qhov sib txawv loj ntawm lawv yog li cas lawv tuav cov ntaub ntawv. Relational databases are structured.Non-relational databases are document-oriented. Qhov no hu ua cov ntaub ntawv hom cia tso cai ntau 'qeb' ntawm cov ntaub ntawv khaws cia hauv ib qho kev tsim lossis Cov Ntaub Ntawv
Dab tsi yog qee qhov tsis zoo ntawm lub sijhawm stamping txoj hauv kev rau kev tswj hwm kev sib raug zoo?
Qhov tsis zoo ntawm lub sij hawm stamping mus kom ze yog tias txhua tus nqi khaws cia hauv cov ntaub ntawv yuav tsum muaj ob lub sij hawm thwj ntxiv: ib qho rau lub sijhawm kawg ntawm daim teb tau nyeem thiab ib qho rau qhov hloov tshiab kawg. Lub sij hawm stamping yog li ua rau kom nco xav tau thiab cov ntaub ntawv ua haujlwm nyiaj siv ua haujlwm