{"id":10021072,"date":"2025-11-10T22:34:29","date_gmt":"2025-11-10T14:34:29","guid":{"rendered":"https:\/\/itmax.cn\/?p=10021072"},"modified":"2025-11-10T22:34:29","modified_gmt":"2025-11-10T14:34:29","slug":"%e4%b8%ba%e4%bb%80%e4%b9%88%e5%9c%a8-javascript-%e4%b8%ad-nan-nan%ef%bc%9f%e8%83%8c%e5%90%8e%e8%97%8f%e7%9d%80-40-%e5%b9%b4%e7%9a%84%e6%8a%80%e6%9c%af%e6%95%85%e4%ba%8b","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10021072","title":{"rendered":"\u4e3a\u4ec0\u4e48\u5728 JavaScript \u4e2d NaN !== NaN\uff1f\u80cc\u540e\u85cf\u7740 40 \u5e74\u7684\u6280\u672f\u6545\u4e8b"},"content":{"rendered":"

1. \u524d\u8a00<\/h2>\n

\u521d\u5b66 JavaScript \u7684\u65f6\u5019\uff0c\u7ecf\u5e38\u4f1a\u9047\u5230\u4e00\u4e9b\u4ee4\u4eba\u56f0\u60d1\u7684\u73b0\u8c61\uff0c\u6bd4\u5982\uff1a<\/p>\n

console.log(NaN === NaN); \/\/ false\nconsole.log(NaN !== NaN); \/\/ true<\/code><\/pre>\n
\u4e3a\u4ec0\u4e48\u4e00\u4e2a\u503c\u4f1a\u4e0d\u7b49\u4e8e\u5b83\u81ea\u5df1\u5462\uff1f<\/p>\n
\u4eca\u5929\uff0c\u6211\u4eec\u5c31\u6765\u6df1\u5165\u63a2\u7a76\u8fd9\u4e2a\u95ee\u9898\u3002<\/p>\n
2. NaN \u7684\u672c\u8d28\uff1a\u4e00\u4e2a\u7279\u6b8a\u7684\u201c\u6570\u5b57\u201d<\/h2>\n
NaN \u5176\u5b9e\u662f Not a Number<\/code> \u7684\u7f29\u5199\uff0c\u8868\u793a\u5b83\u4e0d\u662f\u4e00\u4e2a\u6570\u5b57\u3002\u4f46 NaN \u7684\u7c7b\u578b\u5374\u662f number<\/code>\uff1a<\/p>\n
console.log(typeof NaN); \/\/ "number"<\/code><\/pre>\n
\u6240\u4ee5\u4f60\u53ef\u4ee5\u628a NaN \u7406\u89e3\u4e3a\u4e00\u4e2a\u6570\u5b57\u7c7b\u578b\u7684\u7279\u6b8a\u503c\u3002<\/p>\n
\u5f53\u4f60\u5c1d\u8bd5\u5c06\u975e\u6570\u5b57\u5b57\u7b26\u4e32\u8f6c\u6362\u4e3a\u6570\u5b57\uff0c\u6216\u8005\u8fdb\u884c\u65e0\u6548\u7684\u6570\u5b66\u8fd0\u7b97\u65f6\uff0c\u5c31\u4f1a\u5f97\u5230 NaN\uff1a<\/p>\n
+"oops"; \/\/ NaN\n0 \/ 0; \/\/ NaN<\/code><\/pre>\n
\u800c\u5f53 NaN \u51fa\u73b0\u5728\u6570\u5b66\u8fd0\u7b97\u4e2d\u65f6\uff0c\u5b83\u4f1a\u5bfc\u81f4\u6240\u6709\u8fd0\u7b97\u7ed3\u679c\u90fd\u662f NaN\uff1a<\/p>\n
console.log(NaN + 1); \/\/ NaN\nconsole.log(NaN - 1); \/\/ NaN\nconsole.log(Math.max(NaN, 5)); \/\/ NaN<\/code><\/pre>\n
3. \u6df1\u5165\u5e95\u5c42\uff1aIEEE 754 \u6807\u51c6\u7684\u6545\u4e8b<\/h2>\n
\u8981\u7406\u89e3 NaN !== NaN \u7684\u6839\u6e90\uff0c\u6211\u4eec\u9700\u8981\u56de\u5230 1985 \u5e74\u3002<\/p>\n
\u5f53\u65f6\uff0cIEEE \u53d1\u5e03\u4e86 754 \u53f7\u6807\u51c6<\/strong>\u2014\u2014\u4e8c\u8fdb\u5236\u6d6e\u70b9\u6570\u7b97\u672f\u6807\u51c6<\/a>\u3002<\/p>\n
\u8fd9\u4e2a\u6807\u51c6\u5b9a\u4e49\u4e86\u6d6e\u70b9\u6570\u7684\u8868\u793a\u683c\u5f0f\uff0c\u5305\u62ec\u4e00\u4e9b\u7279\u6b8a\u503c\uff1a\u65e0\u7a77\u5927\uff08Infinity\uff09\u3001\u8d1f\u96f6\uff08-0\uff09\u548c NaN\u3002<\/p>\n
IEEE 754 \u6807\u51c6\u89c4\u5b9a\uff0c\u5f53\u6307\u6570\u90e8\u5206\u4e3a 0x7FF \u800c\u5c3e\u6570\u90e8\u5206\u975e\u96f6\u65f6\uff0c\u8fd9\u4e2a\u503c\u8868\u793a NaN\u3002<\/strong><\/p>\n
\u66f4\u91cd\u8981\u7684\u662f\uff0c\u6807\u51c6\u660e\u786e\u8981\u6c42 NaN \u4e0d\u7b49\u4e8e\u81ea\u8eab\u3002<\/strong><\/p>\n
3.1. \u4e3a\u4ec0\u4e48\u4f1a\u8fd9\u6837\u8bbe\u8ba1\u5462\uff1f<\/h3>\n
\u8fd9\u5176\u5b9e\u662f\u4e00\u79cd\u6df1\u601d\u719f\u8651\u7684\u8bbe\u8ba1<\/strong>\uff0c\u800c\u975e\u9519\u8bef\u3002\u4e3b\u8981\u539f\u56e0\u662f\uff1a<\/p>\n
    \n
  1. \u63d0\u4f9b\u9519\u8bef\u68c0\u6d4b\u673a\u5236<\/strong>\uff1a\u5728\u65e9\u671f\u6ca1\u6709 isNaN()<\/code> \u51fd\u6570\u7684\u7f16\u7a0b\u73af\u5883\u4e2d\uff0cx != x<\/code>\u662f\u68c0\u6d4b NaN \u7684\u552f\u4e00\u65b9\u6cd5<\/li>\n
  2. \u903b\u8f91\u4e00\u81f4\u6027<\/strong>\uff1aNaN \u4ee3\u8868\u201c\u4e0d\u662f\u6570\u5b57\u201d\uff0c\u4e00\u4e2a\u975e\u6570\u503c\u786e\u5b9e\u4e0d\u5e94\u8be5\u7b49\u4e8e\u53e6\u4e00\u4e2a\u975e\u6570\u503c\uff0c\u8fd9\u5728\u903b\u8f91\u4e0a\u4e5f\u662f\u901a\u7545\u7684<\/li>\n<\/ol>\n
    3.2. \u8de8\u8bed\u8a00\u7684\u4e00\u81f4\u6027<\/h3>\n
    \u56e0\u6b64 NaN !== NaN<\/code> \u7684\u884c\u4e3a\u4e0d\u4ec5\u5b58\u5728\u4e8e JavaScript\uff0c\u800c\u662f\u8d2f\u7a7f\u6240\u6709\u9075\u5faa IEEE 754 \u6807\u51c6\u7684\u7f16\u7a0b\u8bed\u8a00\uff1a<\/p>\n
    \u4ee5 Python \u4e3a\u4f8b\uff1a<\/strong><\/p>\n
    #Python\n\nimport math\n\nnan = float('nan')\nprint(nan != nan)  # True\nprint(nan == nan)  # False\nprint(math.isnan(nan))  # True<\/code><\/pre>\n
    \u4ee5 C++ \u4e3a\u4f8b\uff1a<\/strong><\/p>\n
    \/\/C++\n\n#include <iostream>\n#include <cmath>\n\nint main() {\n    double nan = NAN;\n    std::cout << (nan != nan) << std::endl;  \/\/ 1 (true)\n    std::cout << (nan == nan) << std::endl;  \/\/ 0 (false)\n    std::cout << std::isnan(nan) << std::endl;  \/\/ 1 (true, proper way)\n    return 0;\n}<\/code><\/pre>\n
    \u4ee5 Rust \u4e3a\u4f8b\uff1a<\/p>\n
    \/\/Rust\n\nfn main() {\n    let nan = f64::NAN;\n    println!("{}", nan != nan);  \/\/ true\n    println!("{}", nan == nan);  \/\/ false\n    println!("{}", nan.is_nan());  \/\/ true (proper way)\n}<\/code><\/pre>\n
    3.3. \u786c\u4ef6\u7ea7\u522b\u7684\u5b9e\u73b0<\/h3>\n
    \u6709\u8da3\u7684\u662f\uff0cNaN \u7684\u6bd4\u8f83\u884c\u4e3a\u4e0d\u662f\u5728 JavaScript \u5f15\u64ce\u5c42\u9762\u5b9e\u73b0\u7684\uff0c\u800c\u662f\u76f4\u63a5\u7531 CPU \u786c\u4ef6\u63d0\u4f9b<\/strong>\u7684\u652f\u6301\u3002\u60f3\u4e00\u60f3\u4e5f\u5f88\u5408\u903b\u8f91\uff0c\u6211\u4eec\u60f3\u8981\u5bf9\u6570\u5b57\u8fdb\u884c\u8fd0\u7b97\uff0cCPU \u4e5f\u662f\u5728\u64cd\u4f5c\u6570\u5b57\uff0c\u6240\u4ee5\u5728 CPU \u4e2d\u8fdb\u884c\u8fd0\u7b97\u4f1a\u662f\u6700\u5feb\u7684!<\/p>\n
    \u5f53\u6211\u4eec\u67e5\u770b JavaScript \u5f15\u64ce\u6e90\u7801\u65f6\uff0c\u4f1a\u53d1\u73b0\u5b83\u4eec\u4f9d\u8d56\u5e95\u5c42\u7cfb\u7edf\u7684\u6807\u51c6\u5e93\uff1a<\/p>\n
    \/\/ Firefox\nbool isNaN() const { return isDouble() && std::isnan(toDouble()); }\n\n\/\/ V8\nif (IsMinusZero(value)) return has_minus_zero();\nif (std::isnan(value)) return has_nan();<\/code><\/pre>\n
    \u90a3 CPU \u662f\u5982\u4f55\u8bc6\u522b NaN \u7684\u5462\uff1f<\/p>\n
    \u4ee5 x86 \u67b6\u6784\u7684 CPU \u4e3a\u4f8b\uff0c\u5b83\u4f1a\u7528\u4e13\u95e8\u7684 \u201c\u6d6e\u70b9\u5bc4\u5b58\u5668\uff08xmm0\uff09\u201d \u5904\u7406\u6d6e\u70b9\u6570\u8fd0\u7b97\uff0c\u8fd8\u4f1a\u7528\u4e00\u6761\u53eb ucomisd \u7684\u6307\u4ee4\u6bd4\u8f83\u4e24\u4e2a\u6d6e\u70b9\u6570 \u2014\u2014 \u5982\u679c\u6bd4\u8f83\u7684\u662f NaN\uff0c\u8fd9\u6761\u6307\u4ee4\u4f1a\u8bbe\u7f6e\u4e00\u4e2a \u201c\u5947\u5076\u6807\u5fd7\u4f4d\uff08PF=1\uff09\u201d\uff0c\u76f8\u5f53\u4e8e\u7ed9 CPU \u53d1\u4fe1\u53f7\uff1a\u201c\u8fd9\u662f NaN\uff0c\u4e0d\u80fd\u6b63\u5e38\u6bd4\u8f83\uff01\u201d<\/p>\n
    \u7b80\u5355\u6765\u8bf4\uff1a\u5f53\u4f60\u5199 NaN === NaN \u65f6\uff0c\u5e95\u5c42 CPU \u5176\u5b9e\u5df2\u7ecf\u5224\u65ad\u51fa \u201c\u8fd9\u4e24\u4e2a\u503c\u7279\u6b8a\u201d\uff0c\u6240\u4ee5\u8fd4\u56de false\u3002<\/p>\n
    \u518d\u76f4\u89c2\u4e00\u70b9\uff0c\u6211\u4eec\u53ef\u4ee5\u7528 C \u8bed\u8a00\u76f4\u63a5\u64cd\u4f5c\u786c\u4ef6\u5bc4\u5b58\u5668\uff0c\u8ba1\u7b97 \u201c0.0\/0.0\u201d\uff08\u8fd9\u4f1a\u751f\u6210 NaN\uff09\uff1a<\/p>\n
    #include <stdio.h>\n#include <stdint.h>\nint main() {\n    double x = 0.0 \/ 0.0;\n    \/\/ \u76f4\u63a5\u8bfb\u53d6 x \u5728\u5185\u5b58\u4e2d\u7684\u4e8c\u8fdb\u5236\u4f4d\n    uint64_t bits = *(uint64_t*)&x;\n    printf("NaN \u7684\u5341\u516d\u8fdb\u5236\u8868\u793a\uff1a0x%016lx\/n", bits);\n    return 0;\n}<\/code><\/pre>\n
    \u8fd0\u884c\u7ed3\u679c\u4f1a\u662f 0xfff8000000000000<\/code>\u2014\u2014 \u8fd9\u6b63\u662f IEEE 754 \u6807\u51c6\u89c4\u5b9a\u7684 NaN \u5b58\u50a8\u683c\u5f0f\uff0c\u548c CPU \u7684\u5904\u7406\u903b\u8f91\u5b8c\u5168\u5bf9\u5e94\u3002<\/p>\n
    4. JavaScript \u4e0d\u80fd\u6ca1\u6709 NaN<\/h2>\n
    \u5728 IEEE 754 \u6807\u51c6\u4e4b\u524d\uff0c\u5404\u786c\u4ef6\u5382\u5546\u6709\u81ea\u5df1\u5904\u7406\u65e0\u6548\u8fd0\u7b97\u7684\u65b9\u5f0f\u3002\u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u50cf 0\/0 \u8fd9\u6837\u7684\u64cd\u4f5c\u4f1a\u76f4\u63a5\u5bfc\u81f4\u7a0b\u5e8f\u5d29\u6e83<\/strong>\u3002<\/p>\n
    \u60f3\u8c61\u4e00\u4e0b\uff0c\u5982\u679c\u6ca1\u6709 NaN\uff1a<\/p>\n
    \/\/ \u6211\u4eec\u9700\u8981\u5bf9\u6bcf\u4e2a\u6570\u5b66\u8fd0\u7b97\u8fdb\u884c\u9632\u5fa1\u6027\u68c0\u67e5\nfunction safeDivide(a, b) {\n  if (b === 0) {\n    throw new Error("Division by zero!");\n  }\n  if (typeof a !== "number" || typeof b !== "number") {\n    throw new Error("Arguments must be numbers!");\n  }\n  return a \/ b;\n}\n\n\/\/ \u4f7f\u7528try-catch\u5305\u56f4\u6bcf\u4e2a\u53ef\u80fd\u51fa\u9519\u7684\u8fd0\u7b97\ntry {\n  const result = safeDivide(10, 0);\n} catch (e) {\n  \/\/ \u5904\u7406\u9519\u8bef...\n}<\/code><\/pre>\n
    \u800c\u6709\u4e86 NaN\uff0c\u4ee3\u7801\u53d8\u5f97\u7b80\u6d01\u800c\u5b89\u5168\uff1a<\/p>\n
    function divide(a, b) {\n  return a \/ b; \/\/ \u8ba9\u786c\u4ef6\u5904\u7406\u8fb9\u754c\u60c5\u51b5\n}\n\nconst result = divide(10, 0); \/\/ Infinity\nconst invalidResult = 0 \/ 0; \/\/ NaN\n\nif (Number.isNaN(invalidResult)) {\n  \/\/ \u5728\u5408\u9002\u7684\u5730\u65b9\u7edf\u4e00\u5904\u7406\u9519\u8bef\n  console.log("\u68c0\u6d4b\u5230\u65e0\u6548\u8ba1\u7b97");\n}<\/code><\/pre>\n
    5. \u5b9e\u9645\u5f00\u53d1\u4e2d\u5982\u4f55\u68c0\u6d4b\uff1f<\/h2>\n
    \u5728\u65e5\u5e38\u5f00\u53d1\u4e2d\uff0c\u6211\u4eec\u5e94\u8be5\u5982\u4f55\u4f7f\u7528 NaN \u5462\uff1f<\/p>\n
    5.1. \u4f7f\u7528 isNaN() \u51fd\u6570\uff08\u4e0d\u63a8\u8350\uff09<\/h3>\n
    console.log(isNaN(NaN)); \/\/ true\nconsole.log(isNaN("hello")); \/\/ true - \u6ce8\u610f\uff1a\u5b57\u7b26\u4e32\u4f1a\u88ab\u5148\u8f6c\u6362\u4e3a\u6570\u5b57<\/code><\/pre>\n
    isNaN()<\/code> \u51fd\u6570\u4f1a\u5148\u5c1d\u8bd5\u5c06\u53c2\u6570\u8f6c\u6362\u4e3a\u6570\u5b57\uff0c\u8fd9\u53ef\u80fd\u5bfc\u81f4\u610f\u5916\u7684\u7ed3\u679c\u3002<\/p>\n
    5.2. \u4f7f\u7528 Number.isNaN()\uff08\u63a8\u8350\uff09<\/h3>\n
    console.log(Number.isNaN(NaN)); \/\/ true\nconsole.log(Number.isNaN("hello")); \/\/ false - \u4e0d\u4f1a\u8fdb\u884c\u7c7b\u578b\u8f6c\u6362<\/code><\/pre>\n
    ES6 \u5f15\u5165\u7684 Number.isNaN()<\/code> \u53ea\u4f1a\u5bf9\u771f\u6b63\u7684 NaN \u503c\u8fd4\u56de true\uff0c\u662f\u66f4\u5b89\u5168\u7684\u9009\u62e9\u3002<\/p>\n
    5.3. \u4f7f\u7528 Object.is() \u65b9\u6cd5<\/h3>\n
    console.log(Object.is(NaN, NaN)); \/\/ true<\/code><\/pre>\n
    ES6 \u7684 Object.is()<\/code> \u65b9\u6cd5\u80fd\u6b63\u786e\u8bc6\u522b NaN\uff0c\u4f46\u5b83\u4f7f\u7528\u4e25\u683c\u76f8\u7b49\u6bd4\u8f83\uff0c\u9002\u7528\u4e8e\u7279\u6b8a\u573a\u666f\u3002<\/p>\n
    6. \u603b\u7ed3<\/h2>\n
    NaN !== NaN \u662f JavaScript \u4e2d\u4e00\u4e2a\u770b\u4f3c\u5947\u602a\u4f46\u5374\u8bbe\u8ba1\u5408\u7406<\/strong>\u7684\u7279\u6027\u3002\u5b83\u80cc\u540e\u662f IEEE 754 \u6807\u51c6\u7684\u6df1\u601d\u719f\u8651\uff0c\u76ee\u7684\u662f\u4e3a\u6d6e\u70b9\u6570\u8fd0\u7b97\u63d0\u4f9b\u4e00\u81f4\u4e14\u53ef\u9760\u7684\u9519\u8bef\u5904\u7406\u673a\u5236\u3002<\/p>\n
    \u5728\u5b9e\u9645\u5f00\u53d1\u4e2d\uff0c\u8bb0\u4f4f\u4ee5\u4e0b\u51e0\u70b9\uff1a<\/p>\n
      \n
    1. \u59cb\u7ec8\u4f7f\u7528Number.isNaN()<\/code> \u800c\u4e0d\u662f isNaN()<\/code> \u6765\u68c0\u6d4b NaN \u503c<\/strong><\/li>\n
    2. \u542b\u6709 NaN \u7684\u6570\u5b66\u8fd0\u7b97\u603b\u4f1a\u4ea7\u751f NaN<\/strong><\/li>\n
    3. \u5229\u7528\u8fd9\u4e00\u7279\u6027**<\/strong>\u5728\u4ee3\u7801\u4e2d\u4f18\u96c5\u5730\u5904\u7406\u9519\u8bef\u60c5\u51b5**<\/li>\n
    4. \u8bb0\u4f4f NaN \u662f\u6570\u5b57\u7c7b\u578b\u7684\u7279\u6b8a\u503c\uff0c\u8fd9\u5728\u7c7b\u578b\u68c0\u67e5\u65f6\u5f88\u91cd\u8981<\/strong><\/li>\n<\/ol>\n
      7. \u53c2\u8003\u94fe\u63a5<\/h2>\n
        \n
      1. NaN, the not-a-number number that isn\u2019t NaN<\/a><\/li>\n
      2. Why NaN !== NaN in JavaScript (and the IEEE 754 story behind it)<\/a><\/li>\n<\/ol>\n
        https:\/\/segmentfault.com\/a\/1190000047387639<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
        1. \u524d\u8a00 \u521d\u5b66 JavaScript \u7684\u65f6\u5019\uff0c\u7ecf\u5e38\u4f1a\u9047\u5230\u4e00\u4e9b\u4ee4\u4eba\u56f0\u60d1\u7684\u73b0\u8c61\uff0c\u6bd4\u5982\uff1a console.log( […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-10021072","post","type-post","status-publish","format-standard","hentry","category-share"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10021072","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10021072"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10021072\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10021072"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10021072"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10021072"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}