{"id":124754,"date":"2020-06-26T22:13:02","date_gmt":"2020-06-26T14:13:02","guid":{"rendered":"http:\/\/4563.org\/?p=124754"},"modified":"2020-06-26T22:13:02","modified_gmt":"2020-06-26T14:13:02","slug":"%e5%a6%82%e4%bd%95%e4%bb%a5-node-js-%e6%96%b9%e5%bc%8f%e7%bc%96%e5%86%99%e5%8d%95%e4%be%8b","status":"publish","type":"post","link":"http:\/\/4563.org\/?p=124754","title":{"rendered":"\u5982\u4f55\u4ee5 Node.js \u65b9\u5f0f\u7f16\u5199\u5355\u4f8b"},"content":{"rendered":"<div>\n<div>\n<div>\n<h1>                  \u5982\u4f55\u4ee5 Node.js \u65b9\u5f0f\u7f16\u5199\u5355\u4f8b               <\/h1>\n<p> <\/p>\n<div>\n<div> <span>\u8cc7\u6df1\u5927\u4f6c : xihua2018 <\/span>  <span><i><\/i> 5<\/span> <\/div>\n<div> <\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/p><\/div>\n<div isfirst=\"1\"> <\/p>\n<h1>\u5982\u4f55\u4ee5 Node.js \u65b9\u5f0f\u7f16\u5199\u5355\u4f8b<\/h1>\n<p> <\/p>\n<p>\u6587 \/ Victor &#8211; AfterShip<\/p>\n<p>\u8bd1 \/ \u5434\u5929\u6210 &#8211; AfterShip<\/p>\n<h2>\u95ee\u9898\u63cf\u8ff0<\/h2>\n<p>\u4ee5\u4e0b\u9762\u8fd9\u79cd\u65b9\u5f0f\uff0c\u5199\u5355\u4f8b\u5f88\u5bb9\u6613\uff1a<\/p>\n<pre><code>let someModule  async getSomeModule() {     if (!someModule) {         someModule = await someAsyncOperationsToInitializeModule()     }     return someModule }  module.exports = getSomeModule <\/code><\/pre>\n<p>\u901a\u5e38\u4ee5\u8fd9\u79cd\u65b9\u5f0f\u4f7f\u7528\u5b83\uff1a<\/p>\n<pre><code>\/\/ in async function const getSomeModule = require('.\/getSomeModule') const someModule = await getSomeModule() <\/code><\/pre>\n<p>\u9664\u975e\u4f60\u5e0c\u671b\u5c06\u6a21\u5757\u7684\u52a0\u8f7d\u5ef6\u8fdf\u5230\u521d\u6b21\u8fd0\u884c\u65f6\uff0c\u5426\u5219\u4e0d\u9f13\u52b1\u8fd9\u79cd\u65b9\u5f0f\u3002<\/p>\n<p>\u56e0\u4e3a\uff0c\u8fd9\u5c06\u5e26\u6765\u5f88\u591a\u6ca1\u5fc5\u8981\u7684\u5206\u652f\u4ee3\u7801\uff08\u4f8b\u5982\uff0c<strong>if statement<\/strong> \uff09\uff0c\u5b9e\u9645\u4e0a\u6211\u4eec\u5e0c\u671b\u907f\u514d\u8fd9\u79cd\u4ee3\u7801\u3002\u800c\u4e14\u4f7f\u7528 <code>let<\/code> \u8bed\u6cd5\u5c06\u4f1a\u4e2d\u65ad\u9759\u6001\u4ee3\u7801\u5206\u6790\uff0c\u5bfc\u81f4 IDE \u4e0d\u80fd\u6b63\u786e\u63a8\u5bfc\u51fa <code>someModule<\/code> \u7684\u7c7b\u578b\u3002<\/p>\n<h2>\u89e3\u51b3\u65b9\u6848 A<\/h2>\n<p>\u8bf7\u6ce8\u610f\uff0cnode \u7684\u6a21\u5757\u7cfb\u7edf\u9ed8\u8ba4\u4e3a\u5355\u4f8b\uff08\u6a21\u5757\u5728\u7b2c\u4e00\u6b21 required \u7684\u65f6\u5019\u5c06\u4f1a\u88ab\u7f13\u5b58[1]\uff09\u3002\u6240\u4ee5\u4e00\u65e6\u4e00\u4e2a <code>promise<\/code> \u88ab <code>resolved<\/code> \u5e76\u5bfc\u51fa\uff0c\u65e0\u8bba\u8c01 <code>require<\/code>\uff08\u52a0\u8f7d\uff09 \u6a21\u5757\uff0c\u5b83\u5c06\u59cb\u7ec8\u8fd4\u56de\u7b2c\u4e00\u6b21 <code>resolved<\/code> \u7684\u7ed3\u679c\u3002<\/p>\n<p>\u4ee5\u4e0b\u662f\u53ea\u4f7f\u7528<code>const<\/code>\u6765\u5b9e\u73b0\u7684\u65b9\u5f0f\uff1a<\/p>\n<pre><code>\/\/ NodeJs \u65b9\u5f0f\u7684 async \u5355\u4f8b \/\/ someAsyncOperationsToInitializeModule \u4e3a async function \/\/ \u6ce8\u610f\uff0c\u6b64\u5904\u6267\u884c\u51fd\u6570\uff0c\u672a await const someModule = someAsyncOperationsToInitializeModule()  module.exports = someModule <\/code><\/pre>\n<p>2 \u884c\u4ee3\u7801\uff0c\u5c31\u591f\u4e86\u3002<\/p>\n<p>\u4f60\u8be5\u5982\u4f55\u4f7f\u7528\u8fd9\u4e2a\u6a21\u5757\u5462\uff1f<\/p>\n<pre><code>\/\/ in async function \/\/ \u4e0d\u8981\u7528 \"await getSomeModule()\", \u4f60\u4e0d\u9700\u8981 `()` const getSomeModule = require('.\/getSomeModule') const someModule = await getSomeModule <\/code><\/pre>\n<p><code>someModule<\/code> \u7684\u503c\u7edd\u5bf9\u4e0e [\u95ee\u9898\u63cf\u8ff0] \u4e2d\u63d0\u5230\u7684\u4ee3\u7801\u8fd0\u884c\u7ed3\u679c\u5b8c\u5168\u76f8\u540c\u3002<\/p>\n<p>\u4f60\u53ef\u80fd\u4f1a\u6ce8\u610f\u5230\u6587\u4ef6\u540d\u6700\u597d\u66f4\u6539\u4e3a <code>.\/someModule.js<\/code> \u6216 <code>.\/asyncSomeModule.js<\/code> .<\/p>\n<p>\u53e6\u5916\u4e00\u4e2a\u53ef\u80fd\u4f1a\u63d0\u51fa\u7684\u95ee\u9898\u662f\uff0c\u6211\u4eec\u5df2\u7ecf\u4f7f\u7528\u4e86 <code>await getSomeModule()<\/code> \uff0c\u4f46\u662f\u5728\u5f53\u524d\u65b9\u6848\u4e2d\uff0c\u88ab\u8c03\u6574\u4e3a\u4e86 <code>await getSomeModule<\/code>\u3002\u5982\u679c\u6211\u4eec\u91c7\u7528\u8fd9\u79cd\u89e3\u51b3\u65b9\u6848\uff0c\u5c06\u4f1a\u5bf9\u73b0\u6709\u4ee3\u7801\u9020\u6210\u5f88\u5927\u7684\u5f71\u54cd\u3002<\/p>\n<p>\u5176\u5b9e\uff0c\u53ea\u9700\u8981\u505a\u4e00\u70b9\u70b9\u8c03\u6574\uff0c\u5c31\u53ef\u4ee5\u4fdd\u6301\u4e4b\u524d\u7684\u6587\u4ef6\u547d\u540d\u548c\u8c03\u7528\u65b9\u5f0f\u3002<\/p>\n<h2>\u89e3\u51b3\u65b9\u6848 B<\/h2>\n<pre><code>\/\/ NodeJS \u65b9\u5f0f\u7684 async \u5355\u4f8b  const someModule = someAsyncOperationsToInitializeModule()  module.exports = () =&gt; someModule <\/code><\/pre>\n<p>\u73b0\u5728\uff0c\u4f60\u65e0\u9700\u6539\u53d8\u4efb\u4f55\u5916\u90e8\u4ee3\u7801\u3002\u8fd9\u79cd\u5b9e\u73b0 100% \u5411\u540e\u517c\u5bb9\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u4f60\u65e0\u9700\u6539\u9020\u6a21\u5757\u7684\u8c03\u7528\u65b9\u5f0f\uff0c\u6b63\u5982\u95ee\u9898\u4e2d\u6240\u63d0\u5230\u7684\u8c03\u7528\u65b9\u5f0f\u4e00\u6837\u3002<\/p>\n<pre><code>\/\/ in async function const getSomeModule = require('.\/getSomeModule') const someModule = await getSomeModule() <\/code><\/pre>\n<h2>Show me the Code<\/h2>\n<p>https:\/\/repl.it\/@victoratas\/Singleton-in-Nodejs<\/p>\n<h2>\u8865\u5145\u8d44\u6599<\/h2>\n<p>[1] https:\/\/nodejs.org\/api\/modules.html#modules_caching<\/p>\n<\/p><\/div>\n<div> <b>\u5927\u4f6c\u6709\u8a71\u8aaa<\/b> (<span>1<\/span>)        <\/div>\n<div> <\/div>\n<\/p><\/div>\n<\/p><\/div>\n<ul>\n<li data-pid=\"2139802\" data-uid=\"2\">\n<div>\n<div>\n<div> <span>\u8cc7\u6df1\u5927\u4f6c : jmyz0455 <\/span>  <\/div>\n<div> <i title=\"\u5f15\u7528\"><\/i>  <span>          <\/span> <\/div>\n<\/p><\/div>\n<div>                                                             \u611f\u8c22\u5206\u4eab\uff0c\u4e0d\u8fc7\u8001\u54e5\u4f60\u8fd9\u4e2a\u4e3b\u9898\u6211\u770b\u7740\u6709\u70b9\u8f9b\u82e6\uff0c\u80cc\u666f\u662f\u9ed1\u7684\uff0c\u4ee3\u7801\u5757\u5927\u91cf\u6587\u672c\u662f\u7070\u7684\uff0c\u8fa8\u8bc6\u5ea6\u4e0d\u9ad8\u3002\u8fd9\u662f\u60a8\u81ea\u5df1\u5b9a\u4e49\u7684\u4e3b\u9898\u5417\uff1f                                                            <\/div>\n<\/p><\/div>\n<\/li>\n<li>\n","protected":false},"excerpt":{"rendered":"<p>\u5982\u4f55\u4ee5 Node.js \u65b9\u5f0f\u7f16\u5199\u5355&hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[],"tags":[],"_links":{"self":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/124754"}],"collection":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=124754"}],"version-history":[{"count":0,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/124754\/revisions"}],"wp:attachment":[{"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=124754"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=124754"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=124754"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}