{"id":12211,"date":"2021-01-15T00:00:00","date_gmt":"2021-01-14T16:00:00","guid":{"rendered":"https:\/\/fgchen.com\/wpedu2\/2021\/01\/15\/javascript%e5%bf%ab%e9%80%9f%e5%85%a5%e9%96%80-%e6%b1%ba%e7%ad%96decision-making%e8%88%87%e8%bf%b4%e5%9c%88loops\/"},"modified":"2026-03-30T14:39:27","modified_gmt":"2026-03-30T06:39:27","slug":"javascript%e5%bf%ab%e9%80%9f%e5%85%a5%e9%96%80-%e6%b1%ba%e7%ad%96decision-making%e8%88%87%e8%bf%b4%e5%9c%88loops","status":"publish","type":"post","link":"https:\/\/fgchen.com\/wpedu\/2021\/01\/javascript%e5%bf%ab%e9%80%9f%e5%85%a5%e9%96%80-%e6%b1%ba%e7%ad%96decision-making%e8%88%87%e8%bf%b4%e5%9c%88loops\/","title":{"rendered":"JavaScript\u5feb\u901f\u5165\u9580 – \u6c7a\u7b56(Decision making)\u8207(\u8ff4\u5708loops)"},"content":{"rendered":"

\u689d\u4ef6\u5224\u65b7\/Condition<\/h1>\n\n

if<\/h2>\n\n

\u8a9e\u6cd5\/Syntax<\/h3>\n\n
if (\u689d\u4ef6\u5f0f\u70ba\u771f) {\n  \/\/\u6558\u8ff0\n}\n<\/pre>\n\n
\u6d41\u7a0b\u5716<\/h3>\n\n \n\n
\u7bc4\u4f8b\/Example<\/h3>\n\n
let x = 25;\nif( x > 10 ) {\n    console.log('x is greater than 10');\n}<\/pre>\n\n
if..else<\/h2>\n\n
\u8a9e\u6cd5\/Syntax<\/h3>\n\n
if( \u689d\u4ef6\u5f0f\u70ba\u771f\/true) {\n  \/\/ statement\n} else { \n  \/\/ \u7576\u4e0a\u9762\u7684\u689d\u4ef6\u5f0f\u4e0d\u70ba\u771f(\u5047\/false)\u7684\u8a71\uff0c\u57f7\u884c\u6b64\u5340\u584a\u7684\u6558\u8ff0 \n}<\/pre>\n\n
\u6d41\u7a0b\u5716<\/h3>\n\n \n\n \n\n
\u7bc4\u4f8b\/Example<\/h3>\n\n
let x = 5;\nif (x > 10) {\n    console.log('x is greater than 10');\n} else {\n    console.log('x is less than or equal 10');\n}<\/pre>\n\n
if.. else if … else<\/h2>\n\n
\u8a9e\u6cd5\/Syntax<\/h3>\n\n
if (\u689d\u4ef6\u5f0f1\u70ba\u771f) {\n   \/\/ statments\n} else if (\u689d\u4ef6\u5f0f2\u70ba\u771f) {\n  \/\/ statments\n} else {\n   \/\/ \u4ee5\u4e0a2\u500b\u689d\u4ef6\u5f0f\u90fd\u4e0d\u70ba\u771f\u7684\u8a71\u2026\n}<\/pre>\n\n
\u7bc4\u4f8b\/Example<\/h3>\n\n
let a = 10, \n    b = 20;\nif (a > b) {\n    console.log('a is greater than b');\n} else if (a < b) {\n    console.log('a is less than b');\n} else {\n    console.log('a is equal to b');\n}<\/pre>\n\n
\u4e09\u5143\u904b\u7b97\u5f0f(if… else\u7c21\u5316\u5beb\u6cd5)<\/h2>\n\n
\u8a9e\u6cd5\/Syntax<\/h3>\n\n
\u689d\u4ef6\u5f0f ? \u904b\u7b97\u5f0f1 : \u904b\u7b97\u5f0f2\n<\/pre>\n\n
\u7bc4\u4f8b\/Example<\/h3>\n\n
isLoggedIn ? \"Logout\" : \"Login\";\n<\/pre>\n\n\u82e5isLoggedIn\u9019\u500b\u5e03\u6797\u8b8a\u6578\u662f\u771f\u7684\u8a71\uff0c\u5c07 “Logout”\u503c\u6307\u5b9a\u7d66isLoggedIn \u8b8a\u6578\uff0c\u4e0d\u70ba\u771f\u7684\u8a71\uff0c”Login”\u503c\u6307\u5b9a\u7d66isLoggedIn \u8b8a\u6578\uff0c\u4e5f\u5c31\u662f\u8aaaisLoggedIn\u503c\u662ftrue\u7684\u8a71\uff0cisLoggedIn = “Logout”\uff0c\u82e5isLoggedIn\u503c\u662ffalse\u7684\u8a71\uff0cisLoggedIn = “LogIn”\u3002\n\n \n\n
var allowRegister = age > 18 ? true : false;<\/pre>\n\n\u82e5age\u503c\u5927\u65bc18\u7684\u8a71\uff0c\u5e03\u6797\u503c true \u6307\u5b9a\u7d66 allowRegister\uff0c\u82e5age\u503c\u5c0f\u65bc\u6216\u7b49\u65bc18\u7684\u8a71\uff0c\u5e03\u6797\u503c false \u6307\u5b9a\u7d66 allowRegister\u3002\n\n\u82e5\u6558\u8ff0\u4e0d\u6b621\u884c\u7684\u8a71\uff0c\u53ef\u4ee5\u7528\u4e0b\u9762\u7684\u65b9\u5f0f\u4f86\u5beb\uff1a\n\n
age > 18 ? (\n    alert(\"OK, you can register.\"),\n    redirectTo(\"register.html\");\n) : (\n    stop = true,\n    alert(\"Sorry, you are too young!\")\n);<\/pre>\n\n
Switch-case<\/h2>\n\n
\u8a9e\u6cd5\/Syntax<\/h3>\n\n
switch (expression) {\n    case value_1:\n        statement_1;\n        break;\n    case value_2:\n        statement_2;\n        break;\n    case value_3:\n        statement_3;\n        break;\n    default:\n        default_statement;\n}<\/pre>\n\n\n\n
<\/h1>\n\n
var day = 3;\nvar dayName;\nswitch (day) {\n    case 1:\n        dayName = 'Sunday';\n        break;\n    case 2:\n        dayName = 'Monday';\n        break;\n    case 3:\n        dayName = 'Tuesday';\n        break;\n    case 4:\n        dayName = 'Wednesday';\n        break;\n    case 5:\n        dayName = 'Thursday';\n        break;\n    case 6:\n        dayName = 'Friday';\n        break;\n    case 7:\n        dayName = 'Saturday';\n        break;\n    default:\n        dayName = 'Invalid day';\n}\nconsole.log(dayName); \/\/Tuesday<\/pre>\n\n
\u6bcf\u4e00\u500bcase\u9593\u82e5\u4e0d\u63d2\u5165break\uff0c\u6574\u500b\u7a0b\u5f0f\u6d41\u7a0b\u6703\u5f80\u4e0b\u8d70\uff0c\u4f8b\uff1a<\/p>\n\n
var year = 2016;\nvar month = 2;\nvar dayCount;\nswitch (month) {\n    case 1:\n    case 3:\n    case 5:\n    case 7:\n    case 8:\n    case 10:\n    case 12:\n        dayCount = 31;\n        break;\n    case 4:\n    case 6:\n    case 9:\n    case 11:\n        dayCount = 30;\n        break;\n    case 2:\n        if (((year % 4 == 0) && !(year % 100 == 0)) || (year % 400 == 0))\n            dayCount = 29;\n        else\n            dayCount = 28;\n        break;\n    default:\n        dayCount = -1; \/\/ invalid month\n}\n\nconsole.log(dayCount); \/\/29<\/pre>\n\n \n\n
\u8ff4\u5708Loops<\/b><\/h1>\n\n
\u8a9e\u6cd5\/Syntax<\/h3>\n\nfor (\u521d\u59cb\u6558\u8ff0\uff0c\u8ff4\u5708\u9032\u5165\u524d\u6240\u8981\u57f7\u884c\u7684\u6558\u8ff0; \u8ff4\u5708\u9032\u5165\u7684\u689d\u4ef6\u6558\u8ff0; \u6bcf\u6b21\u8ff4\u5708\u57f7\u884c\u5b8c\u6240\u8981\u57f7\u884c\u7684\u6558\u8ff0) { <\/b>\n\n\/\/\u8ff4\u5708\u5340\u584a<\/b>\n\n}\u00a0<\/b>\n\n\u8ff4\u5708\u6709\u4e09\u7a2e\uff1a\n\nfor \uff0c\u6700\u5e38\u7528\u7684<\/b>\n\n
for (var counter = 1; counter < 5; counter++) {\n    console.log('Inside the loop:' + counter);\n}\nconsole.log('Outside the loop:' + counter);\n\n\/*\u8f38\u51fa\nInside the loop:1\nInside the loop:2\nInside the loop:3\nInside the loop:4\nOutside the loop:5\n*\/<\/pre>\n\n \n\n
for (let counter = 1; counter < 5; counter++) {\n    console.log('Inside the loop:' + counter);\n}\nconsole.log('Outside the loop:' + counter);\n\n\/\/Uncaught ReferenceError: counter is not defined\n\/\/let\u6240\u5ba3\u544a\u7684\u8b8a\u6578\u662f\u5340\u584a\u8b8a\u6578\uff0c\u5176\u7bc4\u570d\u50c5\u9650\u65bcfor\u5340\u584a\uff0c\u5340\u584a\u5916\u7121\u6cd5\u4f7f\u7528for\u88cf\u9762\u7684\u5340\u584a\u8b8a\u6578<\/pre>\n\n \n\nfor\u7684\u6d41\u7a0b\u5716\uff1a\n\n\n\n \n\nwhile<\/b>\n\n
let count = 1;\nwhile (count < 10) {\n    console.log(count);\n    count +=2;\n}<\/pre>\n\n \n\ndo while\uff0c\u5148\u505a\u4e00\u6b21\uff0c\u518d\u5224\u65b7\u8981\u4e0d\u8981\u518d\u505a\u2026<\/b>\n\n
let count = 0;\ndo {\n    count++;\n    console.log('count is:' + count);\n} while (count < 10);<\/pre>\n\n \n\nbreak\uff0c\u8df3\u51fa\u5340\u584a { }\uff0c\u76f4\u63a5\u96e2\u958b\u4e00\u500bfor\uff0cwhile\uff0cdo\u2026while\uff0cswitch<\/b>\n\n
for (var i = 1; i < 10; i++) {\n    if (i % 3 == 0) {\n        break;\n    }\n}\nconsole.log(i); \/\/ 3<\/pre>\n\n \n\ncontinue\uff0c\u7565\u904e\u76ee\u524d\u7684\u8ff4\u5708\uff0c\u9032\u884c\u4e0b\u4e00\u500b\u8ff4\u5708\u7684\u9032\u5165\u6c7a\u5b9a\u2026 (\u8ddfbreak\u6574\u500b\u8df3\u51fa\u8ff4\u5708\u6709\u5225)<\/b>\n\n
for ( var i = 1; i < 10; i++) {\n  if ( i % 2 == 0) continue;\n  console.log(i);\n}\n\n\/*\u8f38\u51fa\uff1a\n1\n3\n5\n7\n9\n*\/\n<\/pre>\n\n\u53c3\u8003\u8cc7\u6599\uff1a\n\n
    \n    
  1. JavaScript Loop Which Made Life Easy \u2013 JS Startup<\/a><\/li>\n<\/ol>","protected":false},"excerpt":{"rendered":"
    \u689d\u4ef6\u5224\u65b7\/Condition if \u8a9e\u6cd5\/Syntax if (\u689d\u4ef6\u5f0f\u70ba\u771f) { … <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[266],"tags":[],"class_list":["post-12211","post","type-post","status-publish","format-standard","hentry","category-266"],"_links":{"self":[{"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/posts\/12211","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/comments?post=12211"}],"version-history":[{"count":1,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/posts\/12211\/revisions"}],"predecessor-version":[{"id":13369,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/posts\/12211\/revisions\/13369"}],"wp:attachment":[{"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/media?parent=12211"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/categories?post=12211"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/tags?post=12211"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}