JavaScript: daim ntawv thov piv txwv

Yog hais tias tsis tam sim ntawd ntsaub rau hauv cos syntax thiab semantics ntawm lub JavaScript functionality, yooj yim code qauv no yuav pab rau sai sai kawm tau li cas los txhim kho lub dynamism thiab efficiency ntawm cov nplooj ntawv.

JS - programming lus "hauv lub" browser. JavaScript muaj nws kim heev kev ua hauj lwm nrog nplooj ntawv lub ntsiab, cov thawj cov ntsiab nyob rau hauv lub teb ntawm cov kwv-taw qhia kom paub programming, "yog tau" sib txuas lus nrog cov neeg rau zaub mov, vim hais tias muaj ntau yam ntawm JavaScript code kuaj yog tsis tam sim ntawd muaj kom to taub thiab ua ntawv thov.

General los ntawm tus kheej: yooj yim pib

Programming nyob rau hauv lub browser yog tseem tus hluas, tab sis sai sai sau ib tug high-zoo thiab thawj kev. Cov syntax thiab semantics ntawm lub JavaScript tau txais los ntawm hu ua "pog koob yawg koob", thiab nyob rau hauv ib feem cov functionality thiab practicality ntawm syntax - puas tau txij li thaum lub pre-internet programming lus, tshwj xeeb tshaj yog C / C ++, Pascal.

Browsing nrog JavaScript piv txwv, tsis txhob mus nrhiav kev pab kom sai li sai to taub lub logic kev xav ntawm tus sau phau ntawv thiab lub functionality ntawm cov algorithms - qhov no unpromising ua hauj lwm, zoo siab rau koj tus kheej ntiag tug kev xyaum.

Cias pib nrog lub kev twb kev txuas onload handler rau lub cev tag thiab sau cov tsoos "Nyob zoo" nyob rau hauv ib tug niaj hnub style "I`m npaj txhij".

Cov piv txwv qhia nyob rau hauv JavaScript:

• lub onload kev tshwm sim, tshwm sim tom qab nplooj load yog muab ib tug handler - GoPage () muaj nuj nqi;
• cov nplooj ntawv loads, thiab cov kev tswj muaj nuj nqi tau txais GoPage ();
• ib tug intercom qhia muaj nuj nqi ntawm kev hais lus, uas qhia txog ib tug cov lus nyob rau hauv qhov browser "Kuv npaj txhij";
• Browser qhua xav kom cov tshuaj tiv thaiv.

Lub tswv yim qhia txog cov kev ua uas feem ntau yuav tsum tau ua tom qab lub download tau nplooj thiab pib lub timer.

Heev yooj yim: JS yog heev zoo txuas rau cov nplooj ntawv lub ntsiab. Yog li ntawd, document.getElementById hu qhia ib qhov txuas mus rau ib tug div nrog "scTimer" qhia. Siv cov kev tsim kho dTimer.innerHTML = "tej siv tau HTML code", koj yuav tau dynamically hloov tus txheem ntawm lub div.

Nws yuav tsum tshwj xeeb tshaj yog mloog mus rau lub kev ua yuam kev nyob rau hauv lub cev ntawm lub undesirability ntawm scripts nyob rau hauv JavaScript. Piv txwv ntawm no ua rau tsis zoo txim. Qhov saum toj no code teev alert ( 'Kuv npaj'), thiab cov ua hauj lwm nws tsis. Yuav kom qhia tau tias txhua yam ntawm kab pub apostrophes: hluas thiab ob chav, nyob rau hauv ib tug khub ntawm ib hom tej zaum yuav siv nyob ib leeg, rau lwm yam - ua ib lub cim.

Nyob rau hauv cov ntaub ntawv no nws yuav tsum tau teev, tog twg los alert ( "Kuv npaj txhij"), alert ( 'I`m npaj'), alert ( 'Kuv \' m npaj '), los yog lwm yam kev sib txuas.

Yuam kev nyob rau hauv lub JS-code

Thaum xub thawj yog tus browser, nyob rau cov teg num ntawm lub qhua nws loaded page ntawm qhov chaw, ua ib tug Dom tsob ntoo thiab enabled JavaScript muaj nuj nqi: muab nws lub sij hawm los soj ntsuam qhov loaded page, initialize nws hais, kev tshwm sim handlers, thiab xa mus rau ua kev sib cuag nrog neeg rau zaub mov.

Cais JavaScript (piv txwv), nws yog tsim nyog them sai sai mus code debugging. Qhov no txoj kev yog nce ntog rau tus tsim tawm. Qhov browser nyob rau hauv uas lub chaw ua hauj lwm yog ua, tej zaum yuav qhia no los yog lwm debugging cov cuab yeej, tab sis kev qhia tau hais tias nruj kev ua raws li cov lus syntax, qhov yooj yim thiab laij cov algorithm muaj ib tug ntau dua ntxim rau cov kev kawm tau ntawm kev khiav hauj lwm tau.