{"id":651,"date":"2019-11-04T21:57:18","date_gmt":"2019-11-04T13:57:18","guid":{"rendered":"http:\/\/blog.xrhoujie.com\/?p=651"},"modified":"2019-12-04T22:01:47","modified_gmt":"2019-12-04T14:01:47","slug":"%e7%90%86%e8%a7%a3-asyncawait-%e5%a4%84%e7%90%86%e5%bc%82%e6%ad%a5%e8%bd%ac","status":"publish","type":"post","link":"http:\/\/blog.xrhoujie.com\/?p=651","title":{"rendered":"\u7406\u89e3 async\/await \u5904\u7406\u5f02\u6b65(\u8f6c)"},"content":{"rendered":"<p>\u5148\u8bf4\u4e00\u4e0basync\u7684\u7528\u6cd5\uff0c\u5b83\u4f5c\u4e3a\u4e00\u4e2a\u5173\u952e\u5b57\u653e\u5230\u51fd\u6570\u524d\u9762\uff0c<\/p>\n<div class=\"cnblogs_code\">\n<pre>async function timeout() {\r\n\u3000\u3000return 'hello world';\r\n}<\/pre>\n<\/div>\n<p>\u53ea\u6709\u4e00\u4e2a\u4f5c\u7528, \u5b83\u7684\u8c03\u7528\u4f1a\u8fd4\u56de\u4e00\u4e2apromise\u00a0\u5bf9\u8c61\u3002\u8c03\u7528\u4e00\u4e0b\u770b\u770b\u5c31\u77e5\u9053\u4e86\uff0c\u600e\u4e48\u8c03\u7528\uff1fasync\u00a0\u51fd\u6570\u4e5f\u662f\u51fd\u6570\uff0c\u6240\u4ee5\u5b83\u7684\u8c03\u7528\u548c\u666e\u901a\u51fd\u6570\u7684\u8c03\u7528\u6ca1\u6709\u4ec0\u4e48\u533a\u522b\uff0c\u76f4\u63a5\u52a0\u62ec\u53f7\u8c03\u7528\u5c31\u53ef\u4ee5\u4e86\uff0c\u4e3a\u4e86\u770b\u7ed3\u679c\uff0cconsole.log\u00a0\u4e00\u4e0b<\/p>\n<div class=\"cnblogs_code\">\n<pre>async function timeout() {\r\n    return 'hello world'\r\n}\r\nconsole.log(timeout());<\/pre>\n<\/div>\n<p>\u770b\u4e00\u4e0b\u63a7\u5236\u53f0<\/p>\n<p><img loading=\"lazy\" src=\"https:\/\/img2018.cnblogs.com\/blog\/1013082\/201910\/1013082-20191019134138324-1885815593.png\" alt=\"\" width=\"342\" height=\"87\" \/><\/p>\n<p>async\u51fd\u6570(timeout)\u7684\u8c03\u7528\uff0c\u786e\u5b9e\u8fd4\u56depromise\u00a0\u5bf9\u8c61\uff0c\u5e76\u4e14Promise\u00a0\u8fd8\u6709status\u548cvalue\uff0c\u5982\u679casync\u00a0\u51fd\u6570\u4e2d\u6709\u8fd4\u56de\u503c ,\u5f53\u8c03\u7528\u8be5\u51fd\u6570\u65f6\uff0c\u5185\u90e8\u4f1a\u8c03\u7528Promise.solve()\u00a0\u65b9\u6cd5\u628a\u5b83\u8f6c\u5316\u6210\u4e00\u4e2apromise\u00a0\u5bf9\u8c61\u4f5c\u4e3a\u8fd4\u56de, \u4f46\u5982\u679ctimeout\u00a0\u51fd\u6570\u5185\u90e8\u629b\u51fa\u9519\u8bef\u5462\uff1f<\/p>\n<div class=\"cnblogs_code\">\n<pre>async function timeout() {\r\n    throw new Error('rejected');\r\n}\r\nconsole.log(timeout());<\/pre>\n<\/div>\n<p>\u5c31\u4f1a\u8c03\u7528Promise.reject()\u00a0\u8fd4\u56de\u4e00\u4e2apromise \u5bf9\u8c61\uff0c<\/p>\n<p><img src=\"https:\/\/img2018.cnblogs.com\/blog\/1013082\/201910\/1013082-20191023185120652-1187452863.png\" alt=\"\" \/><\/p>\n<p>\u90a3\u4e48\u8981\u60f3\u83b7\u53d6\u5230async\u00a0\u51fd\u6570\u7684\u6267\u884c\u7ed3\u679c\uff0c\u5c31\u8981\u8c03\u7528promise\u7684then\u00a0\u6216catch\u00a0\u6765\u7ed9\u5b83\u6ce8\u518c\u56de\u8c03\u51fd\u6570\uff0c<\/p>\n<div class=\"cnblogs_code\">\n<pre>async function timeout() {\r\n    return 'hello world'\r\n}\r\ntimeout().then(result =&gt; {\r\n    console.log(result);\r\n})<\/pre>\n<\/div>\n<p>\u5982\u679casync\u00a0\u51fd\u6570\u6267\u884c\u5b8c\uff0c\u8fd4\u56de\u7684promise \u6ca1\u6709\u6ce8\u518c\u56de\u8c03\u51fd\u6570\uff0c\u6bd4\u5982\u51fd\u6570\u5185\u90e8\u505a\u4e86\u4e00\u6b21for\u00a0\u5faa\u73af\uff0c\u4f60\u4f1a\u53d1\u73b0\u51fd\u6570\u7684\u8c03\u7528\uff0c\u5c31\u662f\u6267\u884c\u4e86\u51fd\u6570\u4f53\uff0c\u548c\u666e\u901a\u51fd\u6570\u6ca1\u6709\u533a\u522b\uff0c\u552f\u4e00\u7684\u533a\u522b\u5c31\u662f\u51fd\u6570\u6267\u884c\u5b8c\u4f1a\u8fd4\u56de\u4e00\u4e2apromise\u00a0\u5bf9\u8c61\u3002<\/p>\n<div class=\"cnblogs_code\">\n<pre>async function timeout() {\r\n    for (let index = 0; index &lt; 3; index++) {\r\n        console.log('async '+ index);\r\n    }\r\n}\r\nconsole.log(timeout());\r\nconsole.log('outer')<\/pre>\n<div class=\"cnblogs_code_toolbar\"><\/div>\n<\/div>\n<p>async\u00a0\u5173\u952e\u5b57\u5dee\u4e0d\u591a\u4e86\uff0c\u6700\u91cd\u8981\u7684\u5c31\u662fasync\u51fd\u6570\u7684\u6267\u884c\u4f1a\u8fd4\u56de\u4e00\u4e2apromise\u00a0\u5bf9\u8c61\uff0c\u5e76\u4e14\u628a\u5185\u90e8\u7684\u503c\u8fdb\u884cpromise\u7684\u5c01\u88c5\u3002\u5982\u679cpromise\u5bf9\u8c61\u901a\u8fc7then\u6216catch\u65b9\u6cd5\u53c8\u6ce8\u518c\u4e86\u56de\u8c03\u51fd\u6570\uff0casync\u51fd\u6570\u6267\u884c\u5b8c\u4ee5\u540e\uff0c\u6ce8\u518c\u7684\u56de\u8c03\u51fd\u6570\u5c31\u4f1a\u653e\u5230\u5f02\u6b65\u961f\u5217\u4e2d\uff0c\u7b49\u5f85\u6267\u884c\u3002\u5982\u679c\u53ea\u662fasync,\u00a0 \u548cpromise\u00a0\u5dee\u4e0d\u591a\uff0c\u4f46\u6709\u4e86await\u5c31\u4e0d\u4e00\u6837\u4e86\uff0c await\u00a0\u5173\u952e\u5b57\u53ea\u80fd\u653e\u5230async\u00a0\u51fd\u6570\u91cc\u9762\uff0cawait\u662f\u7b49\u5f85\u7684\u610f\u601d\uff0c\u90a3\u4e48\u5b83\u7b49\u5f85\u4ec0\u4e48\u5462\uff0c\u5b83\u540e\u9762\u8ddf\u7740\u4ec0\u4e48\u5462\uff1f\u5176\u5b9e\u5b83\u540e\u9762\u53ef\u4ee5\u653e\u4efb\u4f55\u8868\u8fbe\u5f0f\uff0c\u4e0d\u8fc7\u6211\u4eec\u66f4\u591a\u7684\u662f\u653e\u4e00\u4e2a\u8fd4\u56depromise\u00a0\u5bf9\u8c61\u7684\u8868\u8fbe\u5f0f\uff0c\u5b83\u7b49\u5f85\u7684\u662fpromise\u00a0\u5bf9\u8c61\u7684\u6267\u884c\u5b8c\u6bd5\uff0c\u5e76\u8fd4\u56de\u7ed3\u679c<\/p>\n<p>\u73b0\u5728\u5199\u4e00\u4e2a\u51fd\u6570\uff0c\u8ba9\u5b83\u8fd4\u56depromise\u00a0\u5bf9\u8c61\uff0c\u8be5\u51fd\u6570\u7684\u4f5c\u7528\u662f2s\u00a0\u4e4b\u540e\u8ba9\u6570\u503c\u4e58\u4ee52<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><\/div>\n<pre>\/\/ 2s \u4e4b\u540e\u8fd4\u56de\u53cc\u500d\u7684\u503c\r\nfunction doubleAfter2seconds(num) {\r\n    return new Promise((resolve, reject) =&gt; {\r\n        setTimeout(() =&gt; {\r\n            resolve(2 * num)\r\n        }, 2000);\r\n    } )\r\n}<\/pre>\n<div class=\"cnblogs_code_toolbar\"><\/div>\n<\/div>\n<p>\u73b0\u5728\u518d\u5199\u4e00\u4e2aasync\u00a0\u51fd\u6570\uff0c\u4ece\u800c\u53ef\u4ee5\u4f7f\u7528await\u00a0\u5173\u952e\u5b57\uff0c await\u00a0\u540e\u9762\u653e\u7f6e\u7684\u5c31\u662f\u8fd4\u56depromise\u5bf9\u8c61\u7684\u4e00\u4e2a\u8868\u8fbe\u5f0f\uff0c\u6240\u4ee5\u5b83\u540e\u9762\u53ef\u4ee5\u5199\u4e0a\u00a0doubleAfter2seconds\u00a0\u51fd\u6570\u7684\u8c03\u7528<\/p>\n<div class=\"cnblogs_code\">\n<pre>async function testResult() {\r\n    let result = await doubleAfter2seconds(30);\r\n    console.log(result);\r\n}<\/pre>\n<\/div>\n<p>\u73b0\u5728\u8c03\u7528testResult\u00a0\u51fd\u6570<\/p>\n<div class=\"cnblogs_code\">\n<pre>testResult();<\/pre>\n<\/div>\n<p>\u6253\u5f00\u63a7\u5236\u53f0\uff0c2s\u00a0\u4e4b\u540e\uff0c\u8f93\u51fa\u4e8660.<\/p>\n<p>\u73b0\u5728\u770b\u770b\u4ee3\u7801\u7684\u6267\u884c\u8fc7\u7a0b\uff0c\u8c03\u7528testResult\u00a0\u51fd\u6570\uff0c\u5b83\u91cc\u9762\u9047\u5230\u4e86await, await\u00a0\u8868\u793a\u7b49\u5f85\uff0c\u4ee3\u7801\u5c31\u6682\u505c\u5230\u8fd9\u91cc\uff0c\u4e0d\u518d\u5411\u4e0b\u6267\u884c\u4e86\uff0c\u5b83\u7b49\u5f85\u540e\u9762\u7684promise\u5bf9\u8c61\u6267\u884c\u5b8c\u6bd5\uff0c\u7136\u540e\u62ff\u5230promise resolve\u00a0\u7684\u503c\u5e76\u8fdb\u884c\u8fd4\u56de\uff0c\u8fd4\u56de\u503c\u62ff\u5230\u4e4b\u540e\uff0c\u5b83\u7ee7\u7eed\u5411\u4e0b\u6267\u884c\u3002\u5177\u4f53\u5230\u00a0\u6211\u4eec\u7684\u4ee3\u7801,\u00a0\u9047\u5230await\u00a0\u4e4b\u540e\uff0c\u4ee3\u7801\u5c31\u6682\u505c\u6267\u884c\u4e86\uff0c\u00a0\u7b49\u5f85doubleAfter2seconds(30) \u6267\u884c\u5b8c\u6bd5\uff0cdoubleAfter2seconds(30)\u00a0\u8fd4\u56de\u7684promise\u00a0\u5f00\u59cb\u6267\u884c\uff0c2\u79d2\u00a0\u4e4b\u540e\uff0cpromise resolve\u00a0\u4e86\uff0c\u00a0\u5e76\u8fd4\u56de\u4e86\u503c\u4e3a60\uff0c\u00a0\u8fd9\u65f6await\u00a0\u624d\u62ff\u5230\u8fd4\u56de\u503c60\uff0c\u00a0\u7136\u540e\u8d4b\u503c\u7ed9result\uff0c\u00a0\u6682\u505c\u7ed3\u675f\uff0c\u4ee3\u7801\u7ee7\u7eed\u6267\u884c\uff0c\u6267\u884c console.log\u8bed\u53e5\u3002<\/p>\n<p>\u5c31\u8fd9\u4e00\u4e2a\u51fd\u6570\uff0c\u6211\u4eec\u53ef\u80fd\u770b\u4e0d\u51faasync\/await\u00a0\u7684\u4f5c\u7528\uff0c\u5982\u679c\u6211\u4eec\u8981\u8ba1\u7b973\u4e2a\u6570\u7684\u503c\uff0c\u7136\u540e\u628a\u5f97\u5230\u7684\u503c\u8fdb\u884c\u8f93\u51fa\u5462\uff1f<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><\/div>\n<pre>async function testResult() {\r\n    let first = await doubleAfter2seconds(30);\r\n    let second = await doubleAfter2seconds(50);\r\n    let third = await doubleAfter2seconds(30);\r\n    console.log(first + second + third);\r\n}<\/pre>\n<\/div>\n<p>6\u79d2\u540e\uff0c\u63a7\u5236\u53f0\u8f93\u51fa220,\u00a0\u6211\u4eec\u53ef\u4ee5\u770b\u5230\uff0c\u5199\u5f02\u6b65\u4ee3\u7801\u5c31\u50cf\u5199\u540c\u6b65\u4ee3\u7801\u4e00\u6837\u4e86\uff0c\u518d\u4e5f\u6ca1\u6709\u56de\u8c03\u5730\u57df\u4e86\u3002<\/p>\n<p>\u8fd9\u91cc\u5f3a\u8c03\u4e00\u4e0b\u7b49\u5f85\uff0c\u5f53js\u5f15\u64ce\u5728\u7b49\u5f85promise resolve\u00a0\u7684\u65f6\u5019\uff0c\u5b83\u5e76\u6ca1\u6709\u771f\u6b63\u7684\u6682\u505c\u5de5\u4f5c\uff0c\u5b83\u53ef\u4ee5\u5904\u7406\u5176\u5b83\u7684\u4e00\u4e9b\u4e8b\u60c5\uff0c\u5982\u679c\u6211\u4eec\u5728testResult\u51fd\u6570\u7684\u8c03\u7528\u540e\u9762\uff0cconsole.log\u00a0\u4e00\u4e0b\uff0c\u4f60\u53d1\u73b0 \u540e\u9762console.log\u7684\u4ee3\u7801\u5148\u6267\u884c\u3002<\/p>\n<div class=\"cnblogs_code\">\n<pre>async function testResult() {\r\n    let first = await doubleAfter2seconds(30);\r\n    let second = await doubleAfter2seconds(50);\r\n    let third = await doubleAfter2seconds(30);\r\n    console.log(first + second + third);\r\n}\r\n\r\ntestResult();\r\nconsole.log('\u5148\u6267\u884c');<\/pre>\n<div class=\"cnblogs_code_toolbar\"><\/div>\n<\/div>\n<p>\u603b\u7ed3\uff1aawait\u5173\u952e\u5b57\u53ea\u80fd\u653e\u5230async\u51fd\u6570\u91cc\u9762\uff0c\u901a\u8fc7await\u5f97\u5230\u5c31\u662fPromise\u8fd4\u56de\u7684\u5185\u5bb9\uff1b\u5f53\u7136\u4e5f\u80fd\u901a\u8fc7then()\u53bb\u83b7\u53d6\uff0c\u82e5\u901a\u8fc7then()\u83b7\u53d6\u4e86\u5219\u5c31\u65e0Promise\u8fd4\u56de\u4e86\uff0c\u63a5\u53d7\u53d8\u91cf\u4e3aundefined\u3002\u56e0\u4e3aPromise\u72b6\u6001\u53ea\u80fd\u4ecepending\u6539\u53d8\u4e00\u6b21<\/p>\n<p>&nbsp;<\/p>\n<p>\u539f\u6587\u5730\u5740\uff1ahttps:\/\/www.cnblogs.com\/SamWeb\/p\/8417940.html<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5148\u8bf4\u4e00\u4e0basync\u7684\u7528\u6cd5\uff0c\u5b83\u4f5c\u4e3a\u4e00\u4e2a\u5173\u952e\u5b57\u653e\u5230\u51fd\u6570\u524d\u9762\uff0c async function timeout() { [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":180,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[10],"tags":[19],"_links":{"self":[{"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=\/wp\/v2\/posts\/651"}],"collection":[{"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=651"}],"version-history":[{"count":1,"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=\/wp\/v2\/posts\/651\/revisions"}],"predecessor-version":[{"id":652,"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=\/wp\/v2\/posts\/651\/revisions\/652"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=\/wp\/v2\/media\/180"}],"wp:attachment":[{"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=651"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=651"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/blog.xrhoujie.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=651"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}