{"id":481,"date":"2013-06-25T17:44:57","date_gmt":"2013-06-25T09:44:57","guid":{"rendered":"https:\/\/yanjingang.com\/blog\/?p=481"},"modified":"2016-03-09T17:51:48","modified_gmt":"2016-03-09T09:51:48","slug":"%e8%b0%88%e8%b0%88js%e7%9a%84%e5%85%a8%e5%b1%80%e5%8f%98%e9%87%8f%e8%b7%9f%e5%b1%80%e9%83%a8%e5%8f%98%e9%87%8f","status":"publish","type":"post","link":"https:\/\/yanjingang.com\/blog\/?p=481","title":{"rendered":"\u8c08\u8c08JS\u7684\u5168\u5c40\u53d8\u91cf\u8ddf\u5c40\u90e8\u53d8\u91cf"},"content":{"rendered":"

\u4eca\u5929\u516c\u53f8\u4e00\u4e2a\u5b9e\u4e60\u5c0f\u59b9\u5b50\u95ee\u6211\u4e24\u6bb5JS\u4ee3\u7801\u7684\u533a\u522b\uff1a<\/p>\n

\n
\n
\n

[javascript]<\/b><\/p>\n<\/div>\n<\/div>\n

    \n
  1. <script\u00a0type=“text\/javascript”<\/span>><\/li>\n
  2. \u00a0var<\/span>\u00a0a\u00a0=\u00a0“Hello”<\/span>;<\/li>\n
  3. \u00a0function<\/span>\u00a0test(){<\/li>\n
  4. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0var<\/span>\u00a0a;<\/li>\n
  5. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(a);<\/li>\n
  6. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0a\u00a0=\u00a0“World”<\/span>;<\/li>\n
  7. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(a);<\/li>\n
  8. \u00a0}<\/li>\n
  9. <\/script><\/li>\n<\/ol>\n<\/div>\n
    \n
    \n
    \n

    [javascript]<\/b><\/p>\n<\/div>\n<\/div>\n

      \n
    1. <script\u00a0type=“text\/javascript”<\/span>><\/li>\n
    2. \u00a0var<\/span>\u00a0a\u00a0=\u00a0“Hello”<\/span>;<\/li>\n
    3. \u00a0function<\/span>\u00a0test(){<\/li>\n
    4. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(a);<\/li>\n
    5. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0a\u00a0=\u00a0“World”<\/span>;<\/li>\n
    6. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(a);<\/li>\n
    7. \u00a0}<\/li>\n
    8. <\/script><\/li>\n<\/ol>\n<\/div>\n

      \u6211\u60f3\uff0c\u597d\u7b80\u5355\u5440\uff0c\u4e0d\u5c31\u662f\u5168\u5c40\u53d8\u91cf\u8ddf\u5c40\u90e8\u53d8\u91cf\u7684scope\u95ee\u9898\u5417\uff1f\u6211\u8bf4:”\u5f53\u5168\u5c40\u53d8\u91cf\u8ddf\u5c40\u90e8\u53d8\u91cf\u91cd\u540d\u65f6\uff0c\u5c40\u90e8\u53d8\u91cf\u7684scope\u4f1a\u8986\u76d6\u6389\u5168\u5c40\u53d8\u91cf\u7684scope\uff0c\u5f53\u79bb\u5f00\u5c40\u90e8\u53d8\u91cf\u7684scope\u540e\uff0c\u53c8\u91cd\u56de\u5230\u5168\u5c40\u53d8\u91cf\u7684scope\u3002\u6240\u4ee5\u4e24\u6bb5\u4ee3\u7801\u8fd0\u884c\u7684\u7ed3\u679c\u5206\u522b\u4e3a\uff1a1) undefined World 2) Hello World\u3002\u7136\u540e\u6211\u968f\u610f\u7f16\u4e86\u5982\u4e0b\u4e00\u4e2a\u4f8b\u5b50\u7ed9\u5979\uff1a<\/p>\n

      \n
      \n
      \n

      [javascript]<\/b><\/p>\n<\/div>\n<\/div>\n

        \n
      1. <script><\/li>\n
      2. \u00a0\u00a0\u00a0var<\/span>\u00a0a\u00a0=1;<\/li>\n
      3. \u00a0\u00a0\u00a0function<\/span>\u00a0test(){<\/li>\n
      4. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(a);<\/li>\n
      5. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0var<\/span>\u00a0a\u00a0=\u00a02;<\/li>\n
      6. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(a);<\/li>\n
      7. \u00a0\u00a0\u00a0}<\/li>\n
      8. \u00a0\u00a0\u00a0test();<\/li>\n
      9. \u00a0\u00a0\u00a0alert(a);<\/li>\n
      10. <\/script><\/li>\n<\/ol>\n<\/div>\n

        \u5927\u5bb6\u731c\u7ed3\u679c\u7b49\u4e8e\u591a\u5c11\uff1f\u662f\u8f93\u51fa1 2 1 \u5417\uff1f\u55ef\u55ef\uff0c\u5f53\u6211\u628a\u6d4b\u8bd5case\u53d1\u7ed9\u5979\u4e4b\u524d\u4e5f\u662f\u8fd9\u4e48\u8ba4\u4e3a\u7684\uff0c\u4f46\u6d4b\u8bd5\u8f93\u51fa\u540e\u2026\u2026\u8fd0\u884c\u7ed3\u679c\u662f undefined 2 1\u3002\u5f53\u65f6\u767e\u601d\u4e0d\u5f97\u5176\u89e3\uff0c\u6240\u4ee5\u75db\u4e0b\u82e6\u529f\uff0c\u5b66\u4e60+\u6d4b\u8bd5\uff0c\u603b\u7ed3\u5982\u4e0b\uff1a<\/p>\n

        \u4e00\u3001Javascript\u7684\u53d8\u91cf\u7684scope\u662f\u6839\u636e\u65b9\u6cd5\u5757\u6765\u5212\u5206\u7684\uff08\u4e5f\u5c31\u662f\u8bf4\u4ee5function\u7684\u4e00\u5bf9\u5927\u62ec\u53f7\uff5b \uff5d\u6765\u5212\u5206\uff09\u3002\u5207\u8bb0\uff0c\u662ffunction\u5757\uff0c\u800cfor\u3001while\u3001if\u5757\u5e76\u4e0d\u662f\u4f5c\u7528\u57df\u7684\u5212\u5206\u6807\u51c6\uff0c\u53ef\u4ee5\u770b\u770b\u4ee5\u4e0b\u51e0\u4e2a\u4f8b\u5b50\uff1a<\/p>\n

        \n
        \n
        \n

        [javascript]<\/b><\/p>\n<\/div>\n<\/div>\n

          \n
        1. <script><\/li>\n
        2. function<\/span>\u00a0test2(){<\/li>\n
        3. \u00a0\u00a0\u00a0\u00a0alert\u00a0(“before\u00a0for\u00a0scope:”<\/span>+i);\u00a0\u00a0\u00a0\u00a0\/\/\u00a0i\u672a\u8d4b\u503c\uff08\u5e76\u4e0d\u662f\u672a\u58f0\u660e\uff01\u4f7f\u7528\u672a\u58f0\u660e\u7684\u53d8\u91cf\u6216\u51fd\u6570\u5168\u629b\u51fa\u81f4\u547d\u9519\u8bef\u800c\u4e2d\u65ad\u811a\u672c\u6267\u884c\uff09<\/span><\/li>\n
        4. <\/li>\n
        5. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u6b64\u65f6i\u7684\u503c\u662funderfined<\/span><\/li>\n
        6. \u00a0\u00a0\u00a0\u00a0for<\/span>(var<\/span>\u00a0i=0;i<3;i++){<\/li>\n
        7. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(“in\u00a0for\u00a0scope:”<\/span>+i);\u00a0\u00a0\/\/\u00a0i\u7684\u503c\u662f\u00a00\u30011\u30012,\u00a0\u5f53i\u4e3a3\u65f6\u8df3\u51fa\u5faa\u73af<\/span><\/li>\n
        8. \u00a0\u00a0\u00a0\u00a0}<\/li>\n
        9. \u00a0\u00a0\u00a0\u00a0alert(“after\u00a0for\u00a0scope:”<\/span>+i);\u00a0\u00a0\/\/\u00a0i\u7684\u503c\u662f3\uff0c\u6ce8\u610f\uff0c\u6b64\u65f6\u5df2\u7ecf\u5728for\u00a0scope\u4ee5\u5916\uff0c\u4f46i\u7684\u503c\u4ecd\u7136\u4fdd\u7559\u4e3a3<\/span><\/li>\n
        10. <\/li>\n
        11. \u00a0\u00a0\u00a0\u00a0while<\/span>(true<\/span>){<\/li>\n
        12. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0var<\/span>\u00a0j\u00a0=\u00a01;<\/li>\n
        13. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0break<\/span>;<\/li>\n
        14. \u00a0\u00a0\u00a0\u00a0}<\/li>\n
        15. \u00a0\u00a0\u00a0\u00a0alert(j);\u00a0\u00a0\u00a0\u00a0\/\/\u00a0j\u7684\u503c\u662f1\uff0c\u6ce8\u610f\uff0c\u6b64\u65f6\u5df2\u7ecf\u5728while\u00a0scope\u4ee5\u5916\uff0c\u4f46j\u7684\u503c\u4ecd\u7136\u4fdd\u7559\u4e3a1<\/span><\/li>\n
        16. <\/li>\n
        17. \u00a0\u00a0\u00a0\u00a0if<\/span>(true<\/span>){<\/li>\n
        18. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0var<\/span>\u00a0k\u00a0=\u00a01;<\/li>\n
        19. \u00a0\u00a0\u00a0\u00a0}<\/li>\n
        20. \u00a0\u00a0\u00a0\u00a0alert(k);\u00a0\u00a0\/\/k\u7684\u503c\u662f1\uff0c\u6ce8\u610f\uff0c\u6b64\u65f6\u5df2\u7ecf\u5728if\u00a0scope\u4ee5\u5916\uff0c\u4f46k\u7684\u503c\u4ecd\u7136\u4fdd\u7559\u4e3a1<\/span><\/li>\n
        21. }<\/li>\n
        22. <\/li>\n
        23. test2();<\/li>\n
        24. \/\/\u82e5\u5728\u6b64\u65f6\uff08function\u00a0scope\u4e4b\u5916\uff09\u518d\u8f93\u51fa\u53ea\u5b58\u5728\u4e8etest2\u00a0\u8fd9\u4e2afunction\u00a0scope\u91cc\u7684\u00a0i\u3001j\u3001k\u53d8\u91cf\u4f1a\u53d1\u751f\u795e\u9a6c\u6548\u679c\u5462\uff1f<\/span><\/li>\n
        25. alert(i);\u00a0\/\/error!\u00a0\u6ca1\u9519\uff0c\u662ferror\uff0c\u539f\u56e0\u662f\u53d8\u91cfi\u672a\u58f0\u660e\uff08\u5e76\u4e0d\u662f\u672a\u8d4b\u503c\uff0c\u533a\u5206test2\u51fd\u6570\u7684\u7b2c\u4e00\u884c\u8f93\u51fa\uff09\uff0c\u5bfc\u81f4\u811a\u672c\u9519\u8bef\uff0c\u7a0b\u5e8f\u5230\u6b64\u7ed3\u675f\uff01<\/span><\/li>\n
        26. alert(“\u8fd9\u884c\u6253\u5370\u8fd8\u4f1a\u8f93\u51fa\u5417\uff1f”<\/span>);\u00a0\/\/\u672a\u6267\u884c<\/span><\/li>\n
        27. alert(j);\u00a0\/\/\u672a\u6267\u884c<\/span><\/li>\n
        28. alert(k);\u00a0\/\/\u672a\u6267\u884c<\/span><\/li>\n
        29. <\/script><\/li>\n<\/ol>\n<\/div>\n

          \u4e8c\u3001Javascript\u5728\u6267\u884c\u524d\u4f1a\u5bf9\u6574\u4e2a\u811a\u672c\u6587\u4ef6\u7684\u58f0\u660e\u90e8\u5206\u505a\u5b8c\u6574\u5206\u6790(\u5305\u62ec\u5c40\u90e8\u53d8\u91cf)\uff0c\u4ece\u800c\u786e\u5b9a\u5b9e\u53d8\u91cf\u7684\u4f5c\u7528\u57df\u3002\u600e\u4e48\u7406\u89e3\u5462\uff1f\u770b\u4e0b\u9762\u4e00\u4e2a\u4f8b\u5b50\uff1a<\/p>\n

          \n
          \n
          \n

          [javascript]<\/b><\/p>\n<\/div>\n<\/div>\n

            \n
          1. <script><\/li>\n
          2. \u00a0\u00a0\u00a0\u00a0var<\/span>\u00a0a\u00a0=1;<\/li>\n
          3. \u00a0\u00a0\u00a0\u00a0function<\/span>\u00a0test(){<\/li>\n
          4. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(a);\u00a0\/\/a\u4e3aundefined!\u00a0\u8fd9\u4e2aa\u5e76\u4e0d\u662f\u5168\u5c40\u53d8\u91cf\uff0c\u8fd9\u662f\u56e0\u4e3a\u5728function\u00a0scope\u91cc\u5df2\u7ecf\u58f0\u660e\u4e86\uff08\u51fd\u6570\u4f53\u5012\u6570\u7b2c4\u884c\uff09\u4e00\u4e2a\u91cd\u540d\u7684\u5c40\u90e8\u53d8\u91cf,<\/span><\/li>\n
          5. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u6240\u4ee5\u5168\u5c40\u53d8\u91cfa\u88ab\u8986\u76d6\u4e86\uff0c\u8fd9\u8bf4\u660e\u4e86Javascript\u5728\u6267\u884c\u524d\u4f1a\u5bf9\u6574\u4e2a\u811a\u672c\u6587\u4ef6\u7684\u5b9a\u4e49\u90e8\u5206\u505a\u5b8c\u6574\u5206\u6790,\u6240\u4ee5\u5728\u51fd\u6570test()\u6267\u884c\u524d,<\/span><\/li>\n
          6. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u51fd\u6570\u4f53\u4e2d\u7684\u53d8\u91cfa\u5c31\u88ab\u6307\u5411\u5185\u90e8\u7684\u5c40\u90e8\u53d8\u91cf.\u800c\u4e0d\u662f\u6307\u5411\u5916\u90e8\u7684\u5168\u5c40\u53d8\u91cf.\u00a0\u4f46\u8fd9\u65f6a\u53ea\u6709\u58f0\u660e\uff0c\u8fd8\u6ca1\u8d4b\u503c\uff0c\u6240\u4ee5\u8f93\u51faundefined\u3002<\/span><\/li>\n
          7. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0a=4<\/li>\n
          8. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(a);\u00a0\u00a0\/\/a\u4e3a4,\u6ca1\u60ac\u5ff5\u4e86\u5427\uff1f\u00a0\u8fd9\u91cc\u7684a\u8fd8\u662f\u5c40\u90e8\u53d8\u91cf\u54e6\uff01<\/span><\/li>\n
          9. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0var<\/span>\u00a0a;\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u5c40\u90e8\u53d8\u91cfa\u5728\u8fd9\u884c\u58f0\u660e<\/span><\/li>\n
          10. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(a);\u00a0\u00a0\/\/a\u8fd8\u662f\u4e3a4,\u8fd9\u662f\u56e0\u4e3a\u4e4b\u524d\u5df2\u628a4\u8d4b\u7ed9a\u4e86<\/span><\/li>\n
          11. \u00a0\u00a0\u00a0\u00a0}<\/li>\n
          12. \u00a0\u00a0\u00a0\u00a0test();<\/li>\n
          13. \u00a0\u00a0\u00a0\u00a0alert(a);\u00a0\/\/a\u4e3a1\uff0c\u8fd9\u91cc\u5e76\u4e0d\u5728function\u00a0scope\u5185\uff0ca\u7684\u503c\u4e3a\u5168\u5c40\u53d8\u91cf\u7684\u503c<\/span><\/li>\n
          14. <\/script><\/li>\n<\/ol>\n<\/div>\n

            \u4e09\uff0c\u5f53\u5168\u5c40\u53d8\u91cf\u8ddf\u5c40\u90e8\u53d8\u91cf\u91cd\u540d\u65f6\uff0c\u5c40\u90e8\u53d8\u91cf\u7684scope\u4f1a\u8986\u76d6\u6389\u5168\u5c40\u53d8\u91cf\u7684scope\uff0c\u5f53\u79bb\u5f00\u5c40\u90e8\u53d8\u91cf\u7684scope\u540e\uff0c\u53c8\u91cd\u56de\u5230\u5168\u5c40\u53d8\u91cf\u7684scope\uff0c\u800c\u5f53\u5168\u5c40\u53d8\u91cf\u9047\u4e0a\u5c40\u90e8\u53d8\u91cf\u65f6\uff0c\u600e\u6837\u4f7f\u7528\u5168\u5c40\u53d8\u91cf\u5462\uff1f\u7528window.globalVariableName\u3002<\/p>\n

            \n
            \n
            \n

            [javascript]<\/b><\/p>\n<\/div>\n<\/div>\n

              \n
            1. <script><\/li>\n
            2. \u00a0\u00a0\u00a0\u00a0var<\/span>\u00a0a\u00a0=1;<\/li>\n
            3. \u00a0\u00a0\u00a0\u00a0function<\/span>\u00a0test(){<\/li>\n
            4. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(window.a);\u00a0\u00a0\/\/a\u4e3a1,\u8fd9\u91cc\u7684a\u662f\u5168\u5c40\u53d8\u91cf\u54e6\uff01<\/span><\/li>\n
            5. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0var<\/span>\u00a0a=2;\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u5c40\u90e8\u53d8\u91cfa\u5728\u8fd9\u884c\u5b9a\u4e49<\/span><\/li>\n
            6. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0alert(a);\u00a0\u00a0\/\/a\u4e3a2,\u8fd9\u91cc\u7684a\u662f\u5c40\u90e8\u53d8\u91cf\u54e6\uff01<\/span><\/li>\n
            7. \u00a0\u00a0\u00a0\u00a0}<\/li>\n
            8. \u00a0\u00a0\u00a0\u00a0test();<\/li>\n
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