JS foreach kwv li cov embodiment

JavaScript syntax muab lub peev xwm los muab cov tsiaj ntawv mus rau hauv arrays thiab cov khoom. Mus saib tau lub ntsiab yuav tsum accessed ntawm indexes thiab lub npe los ntawm ib lub voj voog tswv.

Tab sis nws tsis yog ib txwm tau mus paub cov xov tooj ntawm cov ntsiab nyob rau hauv sau ntawm tsim lub sij hawm thiab yog tsis ib txwm yooj yim rau siv cov syntax muab semantics nyob rau hauv lawv.

classic tsim

Tej voj daim ntawv "rau (var kuv = 0; i

var kuv = 0;
thaum (! typeof aData [i] = 'undefined') {... aData [i]; ... kuv ++; }

thaum lub xov tooj ntawm lub ntsiab yog tsis paub hais tias.

Koj yuav tau tsim ntau algorithms rau filling thiab array ua, tab sis nws yog ntau npaum li cas yooj yim rau siv cov tshiab, niaj hnub nimno variants.

Classic zoo thaum koj yuav tau cov txheej txheem rau questionnaires HR (lub xeem, lub npe, txoj hauj lwm), phaib rau cov khoom (qauv, chaw tsim tshuaj paus, neeg muag khoom, hnub ntawm kev muag khoom), thiab lwm yam ntaub ntawv uas tsis structurally hloov thiab sawv cev rau lub cumulative txaus siab.

Thaum lub array caij nyob rau hauv nws tus kheej yog ib tug kwv los yog cov qauv uas muaj nws tus kheej lub zog thiab txoj kev, tsis tau tiv nrog classic puab kom muaj nuj nqis thiab zoo, thiab yuav siv sij hawm ib tug txawv ntsiab lus array.

Foreach voj

Lub puab yog qhov tseem ceeb zog tiag tiag manifestation array caij. Tsim JS foreach array, nyob rau hauv sib txawv dog dig ntawm lub niaj zaus (saws nyob rau hauv lwm yam lus), version, tso cai rau peb mus muab ib qho kev array ntawm lub sij hawm los qhia lawv lub zog los ntawm lub hnub ntawm nws lub caij.

Piv txwv ib array muaj ib txoj kev (lawv zoo thiab ntau yam ntxwv), thiab lwm array - cov tsheb uas yuav mus tsuas yog nyob rau tej yam kev thiab muaj ntau volume roj tso tsheb hlau luam, i.e. qhov kev ncua deb ntawm cov khoom xyaw yog tseem ceeb heev.

Nyob rau hauv xws li ib embodiment haum algorithm yuav tsum coj raws li ib lub hauv paus, piv txwv li, txoj kev thiab xaiv lub tsheb uas yuav tsum tau tsav tsheb nyob rau hauv nws. Thiab nws yog ib qho zoo, yog hais tias tus txoj kev thiab lub tsheb, hais lus nyob rau hauv qhov kev pab cuam raws li khoom, "pom lawv tus kheej." Qhov no yog ib tug natural daim ntawv thov ntawm cov kwv-taw qhia kom paub programming, uas, cov lwm yam, yuav tsum tau tsis hloov lub algorithm rau hloov txoj kev thiab lub tsheb collections, txiav compensates rau txoj kev kho, tsheb txij nkawm thiab thiaj li nyob

Technically ntawm JS foreach qauv yog yooj yim heev: "aData.forEach (fData);", qhov twg fData - ib tug muaj nuj nqi uas yog thov kom muaj txhua lub caij ntawm lub array aData:

ua fData (tus nqi, index) {sText + = Performance index + '=' + tus nqi + '; '; }.

Yog hais tias lub qhov chaw cov ntaub ntawv yog muaj tuaj raws li nram no:

var aData = [1,2,3,4];
aData.push (11);
aData.push (22);
aData.push (44);
aData.push ( 'kab 1');
aData.push ( 'kab 2');

var sText = '',

qhov tshwm sim ntawm tej kev siv JS foreach yuav:

"0 = 1 1 = 2 2 = 3 3 = 4 4 = 11; 5 = 22, 6 = 44, 7 = kab 1, 8 = kab 2;".

Nta Array khoom

Nruas rau JavaScript - tshwj xeeb. Siv tej yam khoom nyob cov lus no yog ho sib txawv los ntawm implementations nyob rau hauv lwm yam lus. Nruas - qhov no nyob rau hauv nws tus kheej yog ib tug array ntawm lub zog thiab txoj kev. Nrog rau tom kawg yeej ua qhov kev txiav txim, txuag los yog editing nws cov ntsiab lus los yog lwm yam sab nraud khoom, arrays, tsiaj ntawv.

Cov khoom los mus rau hauv lub array li ntas rau lub filmstrip, thaum iterating nyob rau hauv JS foreach khoom lug tsim ib tug tshiab semantics: tsim nce mus nce los kev txiav txim zoo.

Yog li ntawd, txoj kev los ntawm lawv tus kheej yog xaiv tau ib lub tsheb uas muaj peev xwm caij rau lawv, thiab rau hnub kawg yog lim muaj kev. Yog hais tias koj tsis them sai sai, hais tias cov redundancy nyob rau hauv no programming kev xaiv ntau txhim khu kev qha code, cov neeg ua hauj lwm - los mus txiav txim rau lawv txog tus me nyuam - ua JS foreach tsim nyob rau hauv muaj nuj nqis thiab yooj yim tshuaj: nthuav cov tseem khiav ntawm txoj kev, xaiv lub tshuab thiab coj cov me nyuam ntawm cov khoom.

Yog hais tias kev, txoj kev thiab machinery - arrays ntawm cov khoom, lub algorithm yog heev yooj yim zog. Nws yuav zoo li coj txawv txawv hais tias cov emergence of JS foreach qauv raws li ntev ntev nyob rau hauv los. Txawm li cas los, txawm lub simplicity ntawm ib tug taw tes, nyob rau hauv kev xyaum nws yog ib qhov nyuaj rau siv.

Xyaum JS foreach thiab tiag khoom

Xav niaj hnub tsim tawm ua hauj lwm nrog paub tej khoom rau lub cajmeem, tab sis tsis khoom ntawm lub teeb meem tiag tiag. Tsis kheev to taub los ntawm cov neeg ntawm txoj kev tsheb, qhov lawv, qhov kev ncua deb ...

Nruas-taw qhia kom paub programming tau hloov zuj zuj thorny paths, thiab feeb tau lawm coj los ua ib tug pab cuam yam khoom array, cov ntaub ntawv, cov nyees khawm, lawv xaiv lub thawv, thiab lwm yam

Nyob rau hauv tas li ntawd, JS foreach nrog rau lwm yam lus constructs yog ua nyob rau hauv lub qhua browser uas coj nyob rau hauv kev xyaum loj cov kev txwv. Tsis yog txhua txhua tus tsim yog npaj txhij qhia nws code. Pib piv txwv ntawm kev siv ntawm arrays thiab collections ntawm tiag tiag khoom - ib tug zoo txoj kev uas yuav ua kom paub.

Txawm li cas los, cov nyob rau ntawm JavaScript code rau unintended siv tsim tawm muaj ib qho kev indirect feem rau txoj kev loj hlob ntawm pheej tswv yim rau ib tug dynamic thiab real-lub ntiaj teb no cov khoom. JS foreach siv yog tsis tau zoo tag nrho, thiab cov kev loj hlob ntawm lawv semantics nkawd yuav heev pheej coj.