Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression

/
/
gm

Test String

Substitution

Processing...

Code Generator

Generated Code

const regex = /^\d+./gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^\\d+.', 'gm') const str = `1. // #include <conio.h> 2. // #include <stdio.h> 3. #include <iostream> 4. // #include <ctype.h> 5. #include <cstring> 6. using namespace std; 7. class CON_VAT 8. { 9. protected: 10. char *ten; 11. public: 12. CON_VAT() 13. {ten = NULL; 14. } 15. CON_VAT(char *ten1) 16. { 17. strcpy(ten,ten1); 18. } 19. virtual void xung_ten() 20. { } 21. } ; 22. class CON_MEO:public CON_VAT 23. { 24. public: 25. CON_MEO() : CON_VAT() 26. { } 27. CON_MEO(char *ten1) : CON_VAT(ten1) 28. { } 29. virtual void xung_ten() 30. { 31. cout << "\\nToi la chu meo: " << ten ; 32. } 33. }; 34. class CON_CHO:public CON_VAT 35. { 36. public: 37. CON_CHO() : CON_VAT() 38. { } 39. CON_CHO(char *ten1) : CON_VAT(ten1) 40. { } 41. virtual void xung_ten() 42. { 43. cout << "\\nToi la chu cho: " << ten ; 44. } 45. }; 46. class DS_CON_VAT // Danh sach con vat 47. { 48. private: 49. int max_so_con_vat; 50. int so_con_vat; 51. CON_VAT **h ; 52. public: 53. DS_CON_VAT(int max); 54. ~DS_CON_VAT(); 55. int nhap(CON_VAT *c); 56. CON_VAT* xuat(int n); 57. void thong_ke(); 58. } ; 59. DS_CON_VAT::DS_CON_VAT(int max) 60. { 61. max_so_con_vat = max; 62. so_con_vat = 0; 63. h = new CON_VAT*[max]; 64. for (int i=0; i<max; ++i) 65. h[i] = NULL; 66. } 67. DS_CON_VAT::~DS_CON_VAT() 68. { 69. max_so_con_vat = 0; 70. so_con_vat = 0; 71. delete h; 72. } 73. int DS_CON_VAT::nhap(CON_VAT *c) 74. { 75. if (so_con_vat==max_so_con_vat) 76. return 0; 77. int i=0; 78. while (h[i]!=NULL) ++i; 79. h[i]=c; 80. so_con_vat++ ; 81. return (i+1); 82. } 83. CON_VAT* DS_CON_VAT::xuat(int n) 84. { 85. if (n<1 || n > max_so_con_vat) 86. return NULL ; 87. --n ; 88. if (h[n]) 89. { 90. CON_VAT *c = h[n]; 91. h[n]=NULL;/*----------------------???---------------------*/ 92. so_con_vat-- ; 93. return c; 94. } 95. else 96. return NULL; 97. } 98. void DS_CON_VAT::thong_ke() 99. { 100. if (so_con_vat) 101. { 102. cout << "\\n" ; 103. for (int i=0; i<max_so_con_vat; ++i) 104. if (h[i]) 105. h[i]->xung_ten(); 106. } 107. } 108. CON_CHO c1("MUC"); 109. CON_CHO c2("VEN"); 110. CON_CHO c3("LAI"); 111. CON_CHO c4("NHAT"); 112. CON_CHO c5("BONG"); 113. CON_MEO m1("MUOP"); 114. CON_MEO m2("DEN"); 115. CON_MEO m3("TRANG"); 116. CON_MEO m4("TAM THE"); 117. CON_MEO m5("VANG"); 118. DS_CON_VAT d(20); 119. int main() 120. { 121. //clrscr(); 122. d.nhap(&c1); 123. int im2 = d.nhap(&m2); 124. d.nhap(&c3); 125. d.nhap(&m1); 126. int ic4 = d.nhap(&c4); 127. d.nhap(&c5); 128. d.nhap(&m5); 129. d.nhap(&c2); 130. d.nhap(&m3); 131. d.thong_ke(); 132. d.xuat(im2); 133. d.xuat(ic4); 134. d.thong_ke(); 135. //getch(); 136. }`; const subst = ``; // The substituted value will be contained in the result variable const result = str.replace(regex, subst); console.log('Substitution result: ', result);

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions