{"id":132,"date":"2019-06-09T22:50:38","date_gmt":"2019-06-09T22:50:38","guid":{"rendered":"https:\/\/www.369usa.com\/blog\/?p=132"},"modified":"2019-06-09T22:50:38","modified_gmt":"2019-06-09T22:50:38","slug":"%e7%ac%ac%e4%b8%80%e6%89%8b%e5%b0%9d%e8%af%95-react-hook-%e7%9a%84-usereducer","status":"publish","type":"post","link":"https:\/\/www.369usa.com\/blog\/%e7%ac%ac%e4%b8%80%e6%89%8b%e5%b0%9d%e8%af%95-react-hook-%e7%9a%84-usereducer\/","title":{"rendered":"\u7b2c\u4e00\u624b\u5c1d\u8bd5 React Hook \u7684 useReducer"},"content":{"rendered":"<p>\u7b2c\u4e00\u624b\u5c1d\u8bd5 React Hook \u7684 useReducer:<\/p>\n<pre>\r\n\r\nimport React, {useState,useEffect,useReducer} from 'react';\r\nimport ReactDOM from 'react-dom';\r\n\r\n\r\nlet histories = [];\r\n\r\n\r\nconst initialState = {\r\n\tcounter: 10\r\n}\r\n\r\nconst reducer = function(state,action){\r\n\tswitch(action.type){\r\n\t\tcase('INCREMENT'):\r\n\t\t\treturn {...state, counter: state.counter + 1};\r\n\t\tcase('DECREMENT'):\r\n\t\t\treturn {...state, counter: state.counter - 1};\r\n\t\tdefault:\r\n\t\t\tthrow new Error();\r\n\t}\r\n}\r\n\r\n\r\nconst App = function(props){\r\n\t\r\n\tlet _style = {\r\n\t\ttextAlign: 'center',\r\n\t\tmargin: '100px',\r\n\t\tfontSize: '50px',\r\n\t\tlineHeight: '100px'\r\n\t}\r\n\t\r\n\tconst [state,dispatch] = useReducer(reducer,initialState);\r\n\t\r\n\tuseEffect(() =&gt; {\r\n\t\thistories.push(state.counter);\r\n\t\tconsole.log(histories);\r\n\t},[state.counter]);\r\n\t\r\n\treturn (\r\n\t\t&lt;&gt;\r\n\t\t\t&lt;div style={_style}&gt;\r\n\t\t\t\t{state.counter}\r\n\t\t\t\t&lt;br \/&gt;\r\n\t\t\t\t&lt;button onClick={() =&gt; {dispatch({type:'INCREMENT'})}}&gt;Increment&lt;\/button&gt;\r\n\t\t\t\t&lt;button&gt;Just Kidding&lt;\/button&gt;\r\n\t\t\t\t&lt;button onClick={() =&gt; {dispatch({type:'DECREMENT'})}}&gt;Decrement&lt;\/button&gt;\r\n\t\t\t&lt;\/div&gt;\r\n\t\t&lt;\/&gt;\r\n\t)\r\n}\r\n\r\n\r\nReactDOM.render(\r\n\t&lt;App \/&gt;\r\n\t,\r\n\tdocument.getElementById('root')\r\n);\r\n\r\n<\/pre>\n<p>Output:<\/p>\n<pre>\r\n\r\n[10]\r\nmain.js:24870 (2)\u00a0[10, 11]\r\nmain.js:24870 (3)\u00a0[10, 11, 12]\r\nmain.js:24870 (4)\u00a0[10, 11, 12, 13]\r\nmain.js:24870 (5)\u00a0[10, 11, 12, 13, 14]\r\nmain.js:24870 (6)\u00a0[10, 11, 12, 13, 14, 15]\r\nmain.js:24870 (7)\u00a0[10, 11, 12, 13, 14, 15, 16]\r\nmain.js:24870 (8)\u00a0[10, 11, 12, 13, 14, 15, 16, 15]\r\nmain.js:24870 (9)\u00a0[10, 11, 12, 13, 14, 15, 16, 15, 14]\r\nmain.js:24870 (10)\u00a0[10, 11, 12, 13, 14, 15, 16, 15, 14, 13]\r\nmain.js:24870 (11)\u00a0[10, 11, 12, 13, 14, 15, 16, 15, 14, 13, 12]\r\nmain.js:24870 (12)\u00a0[10, 11, 12, 13, 14, 15, 16, 15, 14, 13, 12, 11]\r\nmain.js:24870 (13)\u00a0[10, 11, 12, 13, 14, 15, 16, 15, 14, 13, 12, 11, 10]\r\nmain.js:24870 (14)\u00a0[10, 11, 12, 13, 14, 15, 16, 15, 14, 13, 12, 11, 10, 11]\r\nmain.js:24870 (15)\u00a0[10, 11, 12, 13, 14, 15, 16, 15, 14, 13, 12, 11, 10, 11, 12]\r\n\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>\u7b2c\u4e00\u624b\u5c1d\u8bd5 React Hook \u7684 useReducer: import React, {useState,useEffect,useReducer} from &#8216;react&#8217;; import ReactDOM from &#8216;react-dom&#8217;; let histories = []; const initialState = { counter: 10 } const reducer = function(state,action){ switch(action.type){ case(&#8216;INCREMENT&#8217;): return {&#8230;state, counter: state.counter + 1}; case(&#8216;DECREMENT&#8217;): return {&#8230;state, counter: state.counter &#8211; 1}; default: throw new Error(); } } const App = function(props){ let &hellip; <a href=\"https:\/\/www.369usa.com\/blog\/%e7%ac%ac%e4%b8%80%e6%89%8b%e5%b0%9d%e8%af%95-react-hook-%e7%9a%84-usereducer\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;\u7b2c\u4e00\u624b\u5c1d\u8bd5 React Hook \u7684 useReducer&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-132","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v23.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>\u7b2c\u4e00\u624b\u5c1d\u8bd5 React Hook \u7684 useReducer - \u7ebd\u7ea6\u7f51\u7ad9\u8bbe\u8ba1\u535a\u5ba2<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.369usa.com\/blog\/\u7b2c\u4e00\u624b\u5c1d\u8bd5-react-hook-\u7684-usereducer\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"\u7b2c\u4e00\u624b\u5c1d\u8bd5 React Hook \u7684 useReducer - \u7ebd\u7ea6\u7f51\u7ad9\u8bbe\u8ba1\u535a\u5ba2\" \/>\n<meta property=\"og:description\" content=\"\u7b2c\u4e00\u624b\u5c1d\u8bd5 React Hook \u7684 useReducer: import React, {useState,useEffect,useReducer} from &#039;react&#039;; 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