{"id":31365,"date":"2024-11-25T09:52:51","date_gmt":"2024-11-25T01:52:51","guid":{"rendered":"https:\/\/fwq.ai\/blog\/31365\/"},"modified":"2024-11-25T09:52:51","modified_gmt":"2024-11-25T01:52:51","slug":"js%e4%b8%8etrick%e7%9a%84%e4%bb%a3%e7%a0%81","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/31365\/","title":{"rendered":"JS\u4e0etrick\u7684\u4ee3\u7801"},"content":{"rendered":"

\u8fd9\u6b21\u7ed9\u5927\u5bb6\u5e26\u6765JS\u4e0etrick\u7684\u4ee3\u7801\uff0c\u4f7f\u7528JS\u4e0etrick\u7684\u4ee3\u7801\u7684\u6709\u54ea\u4e9b\uff0c\u4e0b\u9762\u5c31\u662f\u5b9e\u6218\u6848\u4f8b\uff0c\u4e00\u8d77\u6765\u770b\u4e00\u4e0b\u3002<\/p>\n

\u6d6e\u70b9\u6570\u53d6\u6574<\/strong><\/span><\/p>\n

const x = 123.4545;\r\nx >> 0; \/\/ 123\r\n~~x; \/\/ 123\r\nx | 0; \/\/ 123\r\nMath.floor(x); \/\/ 123<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u6ce8\u610f\uff1a\u524d\u4e09\u79cd\u65b9\u6cd5\u53ea\u9002\u7528\u4e8e32\u4e2a\u4f4d\u6574\u6570\uff0c\u5bf9\u4e8e\u8d1f\u6570\u7684\u5904\u7406\u4e0a\u548c Math.floor\u662f\u4e0d\u540c\u7684\u3002<\/p>\n
Math.floor(-12.53); \/\/ -13\r\n-12.53 | 0; \/\/ -12<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u751f\u62106\u4f4d\u6570\u5b57\u9a8c\u8bc1\u7801<\/strong><\/span><\/p>\n
\/\/ \u65b9\u6cd5\u4e00\r\n('000000' + Math.floor(Math.random() * 999999)).slice(-6);\r\n\/\/ \u65b9\u6cd5\u4e8c\r\nMath.random().toString().slice(-6);\r\n\/\/ \u65b9\u6cd5\u4e09\r\nMath.random().toFixed(6).slice(-6);\r\n\/\/ \u65b9\u6cd5\u56db\r\n'' + Math.floor(Math.random() * 999999);<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
16\u8fdb\u5236\u989c\u8272\u4ee3\u7801\u751f\u6210<\/strong><\/span><\/p>\n
(function() {\r\n return '#'+('00000'+\r\n (Math.random()*0x1000000<<0).toString(16)).slice(-6);\r\n})();<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u9a7c\u5cf0\u547d\u540d\u8f6c\u4e0b\u5212\u7ebf<\/strong><\/span><\/p>\n
'componentMapModelRegistry'.match(\/^[a-z][a-z0-9]+|[A-Z][a-z0-9]*\/g).join('_').toLowerCase(); \/\/ component_map_model_registry<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
url\u67e5\u8be2\u53c2\u6570\u8f6cjson\u683c\u5f0f<\/strong><\/span><\/p>\n
\/\/ ES6\r\nconst query = (search = '') => ((querystring = '') => (q => (querystring.split('&').forEach(item => (kv => kv[0] && (q[kv[0]] = kv[1]))(item.split('='))), q))({}))(search.split('?')[1]);\r\n\/\/ \u5bf9\u5e94ES5\u5b9e\u73b0\r\nvar query = function(search) {\r\n if (search === void 0) { search = ''; }\r\n return (function(querystring) {\r\n if (querystring === void 0) { querystring = ''; }\r\n return (function(q) {\r\n  return (querystring.split('&').forEach(function(item) {\r\n  return (function(kv) {\r\n   return kv[0] && (q[kv[0]] = kv[1]);\r\n  })(item.split('='));\r\n  }), q);\r\n })({});\r\n })(search.split('?')[1]);\r\n};\r\nquery('?key1=value1&key2=value2'); \/\/ es6.html:14 {key1: \"value1\", key2: \"value2\"}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u83b7\u53d6URL\u53c2\u6570<\/strong><\/span><\/p>\n
function getQueryString(key){\r\n var reg = new RegExp(\"(^|&)\"+ key +\"=([^&]*)(&|$)\");\r\n var r = window.location.search.substr(1).match(reg);\r\n if(r!=null){\r\n  return unescape(r[2]);\r\n }\r\n return null;\r\n}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
n\u7ef4\u6570\u7ec4\u5c55\u5f00\u6210<\/strong><\/span><\/p>\n
var foo = [1, [2, 3], ['4', 5, ['6',7,[8]]], [9], 10];\r\n\/\/ \u65b9\u6cd5\u4e00\r\n\/\/ \u9650\u5236\uff1a\u6570\u7ec4\u9879\u4e0d\u80fd\u51fa\u73b0`,`\uff0c\u540c\u65f6\u6570\u7ec4\u9879\u5168\u90e8\u53d8\u6210\u4e86\u5b57\u7b26\u6570\u5b57\r\nfoo.toString().split(','); \/\/ [\"1\", \"2\", \"3\", \"4\", \"5\", \"6\", \"7\", \"8\", \"9\", \"10\"]\r\n\/\/ \u65b9\u6cd5\u4e8c\r\n\/\/ \u8f6c\u6362\u540e\u6570\u7ec4\u9879\u5168\u90e8\u53d8\u6210\u6570\u5b57\u4e86\r\neval('[' + foo + ']'); \/\/ [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]\r\n\/\/ \u65b9\u6cd5\u4e09\uff0c\u4f7f\u7528ES6\u5c55\u5f00\u64cd\u4f5c\u7b26\r\n\/\/ \u5199\u6cd5\u592a\u8fc7\u9ebb\u70e6\uff0c\u592a\u8fc7\u6b7b\u677f\r\n[1, ...[2, 3], ...['4', 5, ...['6',7,...[8]]], ...[9], 10]; \/\/ [1, 2, 3, \"4\", 5, \"6\", 7, 8, 9, 10]\r\n\/\/ \u65b9\u6cd5\u56db\r\nJSON.parse(`[${JSON.stringify(foo).replace(\/[|]\/g, '')}]`); \/\/ [1, 2, 3, \"4\", 5, \"6\", 7, 8, 9, 10]\r\n\/\/ \u65b9\u6cd5\u4e94\r\nconst flatten = (ary) => ary.reduce((a, b) => a.concat(Array.isArray(b) ? flatten(b) : b), []);\r\nflatten(foo); \/\/ [1, 2, 3, \"4\", 5, \"6\", 7, 8, 9, 10]\r\n\/\/ \u65b9\u6cd5\u516d\r\nfunction flatten(a) {\r\n return Array.isArray(a) ? [].concat(...a.map(flatten)) : a;<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u6ce8\uff1a\u66f4\u591a\u65b9\u6cd5\u8bf7\u53c2\u8003\u300aHow to flatten nested array in JavaScript?\u300b<\/p>\n
\u65e5\u671f\u683c\u5f0f\u5316<\/strong><\/span><\/p>\n
\/\/ \u65b9\u6cd5\u4e00\r\nfunction format1(x, y) {\r\n var z = {\r\n y: x.getFullYear(),\r\n M: x.getMonth() + 1,\r\n d: x.getDate(),\r\n h: x.getHours(),\r\n m: x.getMinutes(),\r\n s: x.getSeconds()\r\n };\r\n return y.replace(\/(y+|M+|d+|h+|m+|s+)\/g, function(v) {\r\n return ((v.length > 1 ? \"0\" : \"\") + eval('z.' + v.slice(-1))).slice(-(v.length > 2 ? v.length : 2))\r\n });\r\n}\r\nformat1(new Date(), 'yy-M-d h:m:s'); \/\/ 17-10-14 22:14:41\r\n\/\/ \u65b9\u6cd5\u4e8c\r\nDate.prototype.format = function (fmt) { \r\n var o = {\r\n \"M+\": this.getMonth() + 1, \/\/\u6708\u4efd \r\n \"d+\": this.getDate(), \/\/\u65e5 \r\n \"h+\": this.getHours(), \/\/\u5c0f\u65f6 \r\n \"m+\": this.getMinutes(), \/\/\u5206 \r\n \"s+\": this.getSeconds(), \/\/\u79d2 \r\n \"q+\": Math.floor((this.getMonth() + 3) \/ 3), \/\/\u5b63\u5ea6 \r\n \"S\": this.getMilliseconds() \/\/\u6beb\u79d2 \r\n };\r\n if (\/(y+)\/.test(fmt)){\r\n fmt = fmt.replace(RegExp.$1, (this.getFullYear() + \"\").substr(4 - RegExp.$1.length));\r\n } \r\n for (var k in o){\r\n if (new RegExp(\"(\" + k + \")\").test(fmt)){\r\n  fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : ((\"00\" + o[k]).substr((\"\" + o[k]).length)));\r\n }\r\n }  \r\n return fmt;\r\n}\r\nnew Date().format('yy-M-d h:m:s'); \/\/ 17-10-14 22:18:17<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u8f6c\u4e49<\/strong><\/span><\/p>\n
function htmlspecialchars (str) {\r\n var str = str.toString().replace(\/&\/g, \"&\").replace(\/<\/g, \"<\").replace(\/>\/g, \">\").replace(\/\"\/g, '\"');\r\n return str;\r\n}\r\nhtmlspecialchars('&jfkds<>'); \/\/ \"&jfkds<>\"<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u52a8\u6001\u63d2\u5165js<\/strong><\/span><\/p>\n
function injectScript(src) {\r\n var s, t;\r\n s = document.createElement('script');\r\n s.type = 'text\/javascript';\r\n s.async = true;\r\n s.src = src;\r\n t = document.getElementsByTagName('script')[0];\r\n t.parentNode.insertBefore(s, t);\r\n}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u683c\u5f0f\u5316\u6570\u91cf<\/strong><\/span><\/p>\n
\/\/ \u65b9\u6cd5\u4e00\r\nfunction formatNum (num, n) {\r\n if (typeof num == \"number\") {\r\n num = String(num.toFixed(n || 0));\r\n var re = \/(-?d+)(d{3})\/;\r\n while (re.test(num)) num = num.replace(re, \"$1,$2\");\r\n return num;\r\n }\r\n return num;\r\n}\r\nformatNum(2313123, 3); \/\/ \"2,313,123.000\"\r\n\/\/ \u65b9\u6cd5\u4e8c\r\n'2313123'.replace(\/B(?=(d{3})+(?!d))\/g, ','); \/\/ \"2,313,123\"\r\n\/\/ \u65b9\u6cd5\u4e09\r\nfunction formatNum(str) {\r\n return str.split('').reverse().reduce((prev, next, index) => {\r\n return ((index % 3) ? next : (next + ',')) + prev\r\n });\r\n}\r\nformatNum('2313323'); \/\/ \"2,313,323\"<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u8eab\u4efd\u8bc1\u9a8c\u8bc1<\/strong><\/span><\/p>\n
function chechCHNCardId(sNo) {\r\n if (!this.regExpTest(sNo, \/^[0-9]{17}[X0-9]$\/)) {\r\n return false;\r\n }\r\n sNo = sNo.toString();\r\n var a, b, c;\r\n a = parseInt(sNo.substr(0, 1)) * 7 + parseInt(sNo.substr(1, 1)) * 9 + parseInt(sNo.substr(2, 1)) * 10;\r\n a = a + parseInt(sNo.substr(3, 1)) * 5 + parseInt(sNo.substr(4, 1)) * 8 + parseInt(sNo.substr(5, 1)) * 4;\r\n a = a + parseInt(sNo.substr(6, 1)) * 2 + parseInt(sNo.substr(7, 1)) * 1 + parseInt(sNo.substr(8, 1)) * 6;\r\n a = a + parseInt(sNo.substr(9, 1)) * 3 + parseInt(sNo.substr(10, 1)) * 7 + parseInt(sNo.substr(11, 1)) * 9;\r\n a = a + parseInt(sNo.substr(12, 1)) * 10 + parseInt(sNo.substr(13, 1)) * 5 + parseInt(sNo.substr(14, 1)) * 8;\r\n a = a + parseInt(sNo.substr(15, 1)) * 4 + parseInt(sNo.substr(16, 1)) * 2;\r\n b = a % 11;\r\n if (b == 2) {\r\n c = sNo.substr(17, 1).toUpperCase();\r\n } else {\r\n c = parseInt(sNo.substr(17, 1));\r\n }\r\n switch (b) {\r\n case 0:\r\n  if (c != 1) {\r\n  return false;\r\n  }\r\n  break;\r\n case 1:\r\n  if (c != 0) {\r\n  return false;\r\n  }\r\n  break;\r\n case 2:\r\n  if (c != \"X\") {\r\n  return false;\r\n  }\r\n  break;\r\n case 3:\r\n  if (c != 9) {\r\n  return false;\r\n  }\r\n  break;\r\n case 4:\r\n  if (c != 8) {\r\n  return false;\r\n  }\r\n  break;\r\n case 5:\r\n  if (c != 7) {\r\n  return false;\r\n  }\r\n  break;\r\n case 6:\r\n  if (c != 6) {\r\n  return false;\r\n  }\r\n  break;\r\n case 7:\r\n  if (c != 5) {\r\n  return false;\r\n  }\r\n  break;\r\n case 8:\r\n  if (c != 4) {\r\n  return false;\r\n  }\r\n  break;\r\n case 9:\r\n  if (c != 3) {\r\n  return false;\r\n  }\r\n  break;\r\n case 10:\r\n  if (c != 2) {\r\n  return false;\r\n  };\r\n }\r\n return true;\r\n}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u6d4b\u8bd5\u8d28\u6570<\/strong><\/span><\/p>\n
function isPrime(n) {\r\n return !(\/^.?$|^(..+?)+$\/).test('1'.repeat(n))\r\n}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u7edf\u8ba1\u5b57\u7b26\u4e32\u4e2d\u76f8\u540c\u5b57\u7b26\u51fa\u73b0\u7684\u6b21\u6570<\/strong><\/span><\/p>\n
var arr = 'abcdaabc';\r\nvar info = arr\r\n .split('')\r\n .reduce((p, k) => (p[k]++ || (p[k] = 1), p), {});\r\nconsole.log(info); \/\/{ a: 3, b: 2, c: 2, d: 1 }<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u4f7f\u7528 void0\u6765\u89e3\u51b3 undefined\u88ab\u6c61\u67d3\u95ee\u9898<\/strong><\/span><\/p>\n
undefined = 1;\r\n!!undefined; \/\/ true\r\n!!void(0); \/\/ false<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5355\u884c\u5199\u4e00\u4e2a\u8bc4\u7ea7\u7ec4\u4ef6<\/strong><\/span><\/p>\n
\"\".slice(5 - rate, 10 - rate);<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
JavaScript \u9519\u8bef\u5904\u7406\u7684\u65b9\u5f0f\u7684\u6b63\u786e\u59ff\u52bf<\/strong><\/span><\/p>\n
try {\r\n  something\r\n} catch (e) {\r\n  window.location.href =\r\n    \"http:\/\/stackoverflow.com\/search?q=[js]+\" +\r\n    e.message;\r\n}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u81ea\u6267\u884c\u5199\u6cd5<\/strong><\/span><\/p>\n
( function() {}() );\r\n( function() {} )();\r\n[ function() {}() ];\r\n~ function() {}();\r\n! function() {}();\r\n+ function() {}();\r\n- function() {}();\r\ndelete function() {}();\r\ntypeof function() {}();\r\nvoid function() {}();\r\nnew function() {}();\r\nnew function() {};\r\nvar f = function() {}();\r\n1, function() {}();\r\n1 ^ function() {}();\r\n1 > function() {}();<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u4e24\u4e2a\u6574\u6570\u4ea4\u6362\u6570\u503c<\/strong><\/span><\/p>\n
var a = 20, b = 30;\r\na ^= b;\r\nb ^= a;\r\na ^= b;\r\na; \/\/ 30\r\nb; \/\/ 20<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u6570\u5b57\u5b57\u7b26\u8f6c\u6570\u5b57<\/strong><\/span><\/p>\n
var a = '1';\r\n+a; \/\/ 1<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u6700\u77ed\u7684\u4ee3\u7801\u5b9e\u73b0\u6570\u7ec4\u53bb\u91cd<\/strong><\/span><\/p>\n
[...new Set([1, \"1\", 2, 1, 1, 3])]; \/\/ [1, \"1\", 2, 3]<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u7528\u6700\u77ed\u7684\u4ee3\u7801\u5b9e\u73b0\u4e00\u4e2a\u957f\u5ea6\u4e3am(6)\u4e14\u503c\u90fdn(8)\u7684\u6570\u7ec4<\/strong><\/span><\/p>\n
Array(6).fill(8); \/\/ [8, 8, 8, 8, 8, 8]<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5c06argruments\u5bf9\u8c61\u8f6c\u6362\u6210\u6570\u7ec4<\/strong><\/span><\/p>\n
var argArray = Array.prototype.slice.call(arguments);\r\n\/\/ ES6\uff1a\r\nvar argArray = Array.from(arguments)\r\n\/\/ or\r\nvar argArray = [...arguments];<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u83b7\u53d6\u65e5\u671f\u65f6\u95f4\u7f00<\/strong><\/span><\/p>\n
\/\/ \u83b7\u53d6\u6307\u5b9a\u65f6\u95f4\u7684\u65f6\u95f4\u7f00\r\nnew Date().getTime();\r\n(new Date()).getTime();\r\n(new Date).getTime();\r\n\/\/ \u83b7\u53d6\u5f53\u524d\u7684\u65f6\u95f4\u7f00\r\nDate.now();\r\n\/\/ \u65e5\u671f\u663e\u793a\u8f6c\u6362\u4e3a\u6570\u5b57\r\n+new Date();<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u4f7f\u7528 ~x.indexOf(‘y’)\u6765\u7b80\u5316 x.indexOf(‘y’)>-1<\/strong><\/span><\/p>\n
var str = 'hello world';\r\nif (str.indexOf('lo') > -1) {\r\n \/\/ ...\r\n}\r\nif (~str.indexOf('lo')) {\r\n \/\/ ...\r\n}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u4e24\u8005\u7684\u5dee\u522b\u4e4b\u5904\u5728\u4e8e\u89e3\u6790\u548c\u8f6c\u6362\u4e24\u8005\u4e4b\u95f4\u7684\u7406\u89e3\u3002<\/p>\n
\u89e3\u6790\u5141\u8bb8\u5b57\u7b26\u4e32\u4e2d\u542b\u6709\u975e\u6570\u5b57\u5b57\u7b26\uff0c\u89e3\u6790\u6309\u4ece\u5de6\u5230\u53f3\u7684\u987a\u5e8f\uff0c\u5982\u679c\u9047\u5230\u975e\u6570\u5b57\u5b57\u7b26\u5c31\u505c\u6b62\u3002\u800c\u8f6c\u6362\u4e0d\u5141\u8bb8\u51fa\u73b0\u975e\u6570\u5b57\u5b57\u7b26\uff0c\u5426\u8005\u4f1a\u5931\u8d25\u5e76\u8fd4\u56deNaN\u3002<\/p>\n
var a = '520';\r\nvar b = '520px';\r\nNumber(a); \/\/ 520\r\nparseInt(a); \/\/ 520\r\nNumber(b); \/\/ NaN\r\nparseInt(b); \/\/ 520<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
parseInt\u65b9\u6cd5\u7b2c\u4e8c\u4e2a\u53c2\u6570\u7528\u4e8e\u6307\u5b9a\u8f6c\u6362\u7684\u57fa\u6570\uff0cES5\u9ed8\u8ba4\u4e3a10\u8fdb\u5236\u3002<\/p>\n
parseInt('10', 2); \/\/ 2\r\nparseInt('10', 8); \/\/ 8\r\nparseInt('10', 10); \/\/ 10\r\nparseInt('10', 16); \/\/ 16<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5bf9\u4e8e\u7f51\u4e0a parseInt(0.0000008)\u7684\u7ed3\u679c\u4e3a\u4ec0\u4e48\u4e3a8\uff0c\u539f\u56e0\u5728\u4e8e0.0000008\u8f6c\u6362\u6210\u5b57\u7b26\u4e3a”8e-7″\uff0c\u7136\u540e\u6839\u636e parseInt\u7684\u89e3\u6790\u89c4\u5219\u81ea\u7136\u5f97\u5230”8″\u8fd9\u4e2a\u7ed3\u679c\u3002<\/p>\n
+ \u62fc\u63a5\u64cd\u4f5c\uff0c+x or String(x)\uff1f<\/strong><\/span><\/p>\n
+\u8fd0\u7b97\u7b26\u53ef\u7528\u4e8e\u6570\u5b57\u52a0\u6cd5\uff0c\u540c\u65f6\u4e5f\u53ef\u4ee5\u7528\u4e8e\u5b57\u7b26\u4e32\u62fc\u63a5\u3002\u5982\u679c+\u7684\u5176\u4e2d\u4e00\u4e2a\u64cd\u4f5c\u7b26\u662f\u5b57\u7b26\u4e32(\u6216\u8005\u901a\u8fc7 \u9690\u5f0f\u5f3a\u5236\u8f6c\u6362\u53ef\u4ee5\u5f97\u5230\u5b57\u7b26\u4e32)\uff0c\u5219\u6267\u884c\u5b57\u7b26\u4e32\u62fc\u63a5\uff1b\u5426\u8005\u6267\u884c\u6570\u5b57\u52a0\u6cd5\u3002<\/p>\n
\u9700\u8981\u6ce8\u610f\u7684\u65f6\u5bf9\u4e8e\u6570\u7ec4\u800c\u8a00\uff0c\u4e0d\u80fd\u901a\u8fc7 valueOf()\u65b9\u6cd5\u5f97\u5230\u7b80\u5355\u57fa\u672c\u7c7b\u578b\u503c\uff0c\u4e8e\u662f\u8f6c\u800c\u8c03\u7528 toString()\u65b9\u6cd5\u3002<\/p>\n
[1,2] + [3, 4]; \/\/ \"1,23,4\"<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5bf9\u4e8e\u5bf9\u8c61\u540c\u6837\u4f1a\u5148\u8c03\u7528 valueOf()\u65b9\u6cd5\uff0c\u7136\u540e\u901a\u8fc7 toString()\u65b9\u6cd5\u8fd4\u56de\u5bf9\u8c61\u7684\u5b57\u7b26\u4e32\u8868\u793a\u3002<\/p>\n
var a = {};\r\na + 123; \/\/ \"[object Object]123\"<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5bf9\u4e8e a+””\u9690\u5f0f\u8f6c\u6362\u548c String(a)\u663e\u793a\u8f6c\u6362\u6709\u4e00\u4e2a\u7ec6\u5fae\u7684\u5dee\u522b\uff1a a+”\u4f1a\u5bf9a\u8c03\u7528 valueOf()\u65b9\u6cd5\uff0c\u800c String()\u76f4\u63a5\u8c03\u7528 toString()\u65b9\u6cd5\u3002\u5927\u591a\u6570\u60c5\u51b5\u4e0b\u6211\u4eec\u4e0d\u4f1a\u8003\u8651\u8fd9\u4e2a\u95ee\u9898\uff0c\u9664\u975e\u771f\u9047\u5230\u3002<\/p>\n
var a = {\r\n valueOf: function() { return 42; },\r\n toString: function() { return 4; }\r\n}\r\na + ''; \/\/ 42\r\nString(a); \/\/ 4<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5224\u65ad\u5bf9\u8c61\u7684\u5b9e\u4f8b<\/strong><\/span><\/p>\n
\/\/ \u65b9\u6cd5\u4e00: ES3\r\nfunction Person(name, age) {\r\n if (!(this instanceof Person)) {\r\n  return new Person(name, age);\r\n }\r\n this.name = name;\r\n this.age = age;\r\n}\r\n\/\/ \u65b9\u6cd5\u4e8c: ES5\r\nfunction Person(name, age) {\r\n var self = this instanceof Person ? this : Object.create(Person.prototype);\r\n self.name = name;\r\n self.age = age;\r\n return self;\r\n}\r\n\/\/ \u65b9\u6cd5\u4e09\uff1aES6\r\nfunction Person(name, age) {\r\n if (!new.target) {\r\n  throw 'Peron must called with new';\r\n }\r\n this.name = name;\r\n this.age = age;\r\n}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u6570\u636e\u5b89\u5168\u7c7b\u578b\u68c0\u67e5<\/strong><\/span><\/p>\n
\/\/ \u5bf9\u8c61\r\nfunction isObject(value) {\r\n return Object.prototype.toString.call(value).slice(8, -1) === 'Object'';\r\n}\r\n\/\/ \u6570\u7ec4\r\nfunction isArray(value) {\r\n return Object.prototype.toString.call(value).slice(8, -1) === 'Array';\r\n}\r\n\/\/ \u51fd\u6570\r\nfunction isFunction(value) {\r\n return Object.prototype.toString.call(value).slice(8, -1) === 'Function';\r\n}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u8ba9\u6570\u5b57\u7684\u5b57\u9762\u503c\u770b\u8d77\u6765\u50cf\u5bf9\u8c61<\/p>\n
toString(); \/\/ Uncaught SyntaxError: Invalid or unexpected token\r\n..toString(); \/\/ \u7b2c\u4e8c\u4e2a\u70b9\u53f7\u53ef\u4ee5\u6b63\u5e38\u89e3\u6790\r\n .toString(); \/\/ \u6ce8\u610f\u70b9\u53f7\u524d\u9762\u7684\u7a7a\u683c\r\n(2).toString(); \/\/ 2\u5148\u88ab\u8ba1\u7b97<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5bf9\u8c61\u53ef\u8ba1\u7b97\u5c5e\u6027\u540d(\u4ec5\u5728ES6\u4e2d)<\/strong><\/span><\/p>\n
var suffix = ' name';\r\nvar person = {\r\n ['first' + suffix]: 'Nicholas',\r\n ['last' + suffix]: 'Zakas'\r\n}\r\nperson['first name']; \/\/ \"Nicholas\"\r\nperson['last name']; \/\/ \"Zakas\"<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u6570\u5b57\u56db\u820d\u4e94\u5165<\/strong><\/span><\/p>\n
\/\/ v: \u503c\uff0cp: \u7cbe\u5ea6\r\nfunction (v, p) {\r\n p = Math.pow(10, p >>> 31 ? 0 : p | 0)\r\n v *= p;\r\n return (v + 0.5 + (v >> 31) | 0) \/ p\r\n}\r\nround(123.45353, 2); \/\/ 123.45<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5728\u6d4f\u89c8\u5668\u4e2d\u6839\u636eurl\u4e0b\u8f7d\u6587\u4ef6<\/strong><\/span><\/p>\n
function download(url) {\r\n var isChrome = navigator.userAgent.toLowerCase().indexOf('chrome') > -1;\r\n var isSafari = navigator.userAgent.toLowerCase().indexOf('safari') > -1;\r\n if (isChrome || isSafari) {\r\n  var link = document.createElement('a');\r\n  link.href = url;\r\n  if (link.download !== undefined) {\r\n   var fileName = url.substring(url.lastIndexOf('\/') + 1, url.length);\r\n   link.download = fileName;\r\n  }\r\n  if (document.createEvent) {\r\n   var e = document.createEvent('MouseEvents');\r\n   e.initEvent('click', true, true);\r\n   link.dispatchEvent(e);\r\n   return true;\r\n  }\r\n }\r\n if (url.indexOf('?') === -1) {\r\n  url += '?download';\r\n }\r\n window.open(url, '_self');\r\n return true;\r\n}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5feb\u901f\u751f\u6210UUID<\/strong><\/span><\/p>\n
function uuid() {\r\n var d = new Date().getTime();\r\n var uuid = 'xxxxxxxxxxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(\/[xy]\/g, function(c) {\r\n  var r = (d + Math.random() * 16) % 16 | 0;\r\n  d = Math.floor(d \/ 16);\r\n  return (c == 'x' ? r : (r & 0x3 | 0x8)).toString(16);\r\n });\r\n return uuid;\r\n};\r\nuuid(); \/\/ \"33f7f26656cb-499b-b73e-89a921a59ba6\"<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
JavaScript\u6d6e\u70b9\u6570\u7cbe\u5ea6\u95ee\u9898<\/strong><\/span><\/p>\n
function isEqual(n1, n2, epsilon) {\r\n epsilon = epsilon == undefined ? 10 : epsilon; \/\/ \u9ed8\u8ba4\u7cbe\u5ea6\u4e3a10\r\n return n1.toFixed(epsilon) === n2.toFixed(epsilon);\r\n}\r\n0.1 + 0.2; \/\/ 0.30000000000000004\r\nisEqual(0.1 + 0.2, 0.3); \/\/ true\r\n0.7 + 0.1 + 99.1 + 0.1; \/\/ 99.99999999999999\r\nisEqual(0.7 + 0.1 + 99.1 + 0.1, 100); \/\/ true<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u683c\u5f0f\u5316\u8868\u5355\u6570\u636e<\/strong><\/span><\/p>\n
function formatParam(obj) {\r\n var query = '', name, value, fullSubName, subName, subValue, innerObj, i;\r\n for(name in obj) {\r\n  value = obj[name];\r\n  if(value instanceof Array) {\r\n   for(i=0; i<value.length; ++i) {\r\n    subValue = value[i];\r\n    fullSubName = name + '[' + i + ']';\r\n    innerObj = {};\r\n    innerObj[fullSubName] = subValue;\r\n    query += formatParam(innerObj) + '&';\r\n   }\r\n  }\r\n  else if(value instanceof Object) {\r\n   for(subName in value) {\r\n    subValue = value[subName];\r\n    fullSubName = name + '[' + subName + ']';\r\n    innerObj = {};\r\n    innerObj[fullSubName] = subValue;\r\n    query += formatParam(innerObj) + '&';\r\n   }\r\n  }\r\n  else if(value !== undefined && value !== null)\r\n   query += encodeURIComponent(name) + '=' + encodeURIComponent(value) + '&';\r\n }\r\n return query.length ? query.substr(0, query.length - 1) : query;\r\n}\r\nvar param = {\r\n name: 'jenemy',\r\n likes: [0, 1, 3],\r\n memberCard: [\r\n  { title: '1', id: 1 },\r\n  { title: '2', id: 2 }\r\n ]\r\n}\r\nformatParam(param); \/\/ \"name=12&likes%5B0%5D=0&likes%5B1%5D=1&likes%5B2%5D=3&memberCard%5B0%5D%5Btitle%5D=1&memberCard%5B0%5D%5Bid%5D=1&memberCard%5B1%5D%5Btitle%5D=2&memberCard%5B1%5D%5Bid%5D=2\"<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u521b\u5efa\u6307\u5b9a\u957f\u5ea6\u975e\u7a7a\u6570\u7ec4<\/strong><\/span><\/p>\n
\u5728JavaScript\u4e2d\u53ef\u4ee5\u901a\u8fc7new Array(3)\u7684\u5f62\u5f0f\u521b\u5efa\u4e00\u4e2a\u957f\u5ea6\u4e3a3\u7684\u7a7a\u6570\u7ec4\u3002\u5728\u8001\u7684Chrome\u4e2d\u5176\u503c\u4e3a[undefined x 3]\uff0c\u5728\u6700\u65b0\u7684Chrome\u4e2d\u4e3a[empty x 3]\uff0c\u5373\u7a7a\u5355\u5143\u6570\u7ec4\u3002\u5728\u8001Chrome\u4e2d\uff0c\u76f8\u5f53\u4e8e\u663e\u793a\u4f7f\u7528[undefined, undefined, undefined]\u7684\u65b9\u5f0f\u521b\u5efa\u957f\u5ea6\u4e3a3\u7684\u6570\u7ec4\u3002<\/p>\n
\u4f46\u662f\uff0c\u4e24\u8005\u5728\u8c03\u7528map()\u65b9\u6cd5\u7684\u7ed3\u679c\u662f\u660e\u663e\u4e0d\u540c\u7684<\/p>\n
var a = new Array(3);\r\nvar b = [undefined, undefined, undefined];\r\na.map((v, i) => i); \/\/ [empty \u00d7 3]\r\nb.map((v, i) => i); \/\/ [0, 1, 2]<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u591a\u6570\u60c5\u51b5\u6211\u4eec\u671f\u671b\u521b\u5efa\u7684\u662f\u5305\u542bundefined\u503c\u7684\u6307\u5b9a\u957f\u5ea6\u7684\u7a7a\u6570\u7ec4\uff0c\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u8fd9\u79cd\u65b9\u6cd5\u6765\u8fbe\u5230\u76ee\u7684\uff1a<\/p>\n
var a = Array.apply(null, { length: 3 });\r\na; \/\/ [undefined, undefined, undefined]\r\na.map((v, i) => i); \/\/ [0, 1, 2]<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u603b\u4e4b\uff0c\u5c3d\u91cf\u4e0d\u8981\u521b\u5efa\u548c\u4f7f\u7528\u7a7a\u5355\u5143\u6570\u7ec4\u3002<\/p>\n
\u76f8\u4fe1\u770b\u4e86\u672c\u6587\u6848\u4f8b\u4f60\u5df2\u7ecf\u638c\u63e1\u4e86\u65b9\u6cd5\uff0c\u66f4\u591a\u7cbe\u5f69\u8bf7\u5173\u6ce8\u7c73\u4e91\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n
\u63a8\u8350\u9605\u8bfb\uff1a<\/p>\n<\/p>\n
<\/p>\n
\u4ee5\u4e0a\u5c31\u662fJS\u4e0etrick\u7684\u4ee3\u7801\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
\u8fd9\u6b21\u7ed9\u5927\u5bb6\u5e26\u6765JS\u4e0etrick\u7684\u4ee3\u7801\uff0c\u4f7f\u7528JS\u4e0etrick\u7684\u4ee3\u7801\u7684\u6709\u54ea\u4e9b\uff0c\u4e0b\u9762\u5c31\u662f\u5b9e\u6218\u6848\u4f8b\uff0c\u4e00\u8d77\u6765\u770b\u4e00\u4e0b\u3002 \u6d6e\u70b9\u6570\u53d6\u6574 const x = 123.4545; x >> 0; \/\/ 123 ~~x; \/\/ 123 x | 0; \/\/ 123 Math.floor(x); \/\/ 123 \u767b\u5f55\u540e\u590d\u5236 \u6ce8\u610f\uff1a\u524d\u4e09\u79cd\u65b9\u6cd5\u53ea\u9002\u7528\u4e8e32\u4e2a\u4f4d\u6574\u6570\uff0c\u5bf9\u4e8e\u8d1f\u6570\u7684\u5904\u7406\u4e0a\u548c Math.floor\u662f\u4e0d\u540c\u7684\u3002 Math.floor(-12.53); \/\/ -13 -12.53 | 0; \/\/ -12 \u767b\u5f55\u540e\u590d\u5236 \u751f\u62106\u4f4d\u6570\u5b57\u9a8c\u8bc1\u7801 \/\/ \u65b9\u6cd5\u4e00 (‘000000’ + Math.floor(Math.random() * 999999)).slice(-6); \/\/ \u65b9\u6cd5\u4e8c Math.random().toString().slice(-6); \/\/ \u65b9\u6cd5\u4e09 Math.random().toFixed(6).slice(-6); \/\/ \u65b9\u6cd5\u56db ” + Math.floor(Math.random() * 999999); […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[19],"tags":[],"class_list":["post-31365","post","type-post","status-publish","format-standard","hentry","category-19"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/31365","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=31365"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/31365\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=31365"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=31365"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=31365"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}