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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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

Code Generator

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)(?-i)^[\t ]*((?:[!(]|\w+\(|(?:(?:const|let|var)[\t ]+)?[\w$]+[\t ]*[:=][\t ]*(?:{\w+[\t ]*:[\t ]*)?)?)((?:\([^\r\n)]*\)|\w)[\t ]*=>)`) var str = `!function(){}(); // test1 !function test2(){}(); // test2 (function(){})(); // test3 (function test4(){})(); // test4 test5 = function(){} // test5 test6 = function _test6(){} // test6 let test7 = function(){} // test7 let test8 = function _test8(){} // test8 var test9 = function(){} // test8 var test10 = function _test10(){} // test10 const test11 = function(){} // test11 const test12 = function _test12(){} // test12 myfunc(function(){}) // test13 myfunc(function test14(){}) // test14 let myobj15 = {test15 : function(){}} // test15 let myobj16 = {test16 : function _test16(){}} // test16 var myobj17 = {test17 : function(){}} // test17 var myobj18 = {test18 : function _test18(){}} // test18 const myobj19 = {test19 : function(){}} // test19 const myobj20 = {test20 : function _test20(){}} // test20 !function(a){}(); // test21 !function test22(b){}(); // test22 (function(c){})(); // test23 (function test24(d){})(); // test24 test25 = function(e){} // test25 test26 = function _test26(f){} // test26 let test27 = function(g){} // test27 let test28 = function _test28(h){} // test28 var test29 = function(i){} // test29 var test30 = function _test30(j){} // test30 const test31 = function(k){} // test31 const test32 = function _test32(l){} // test32 myfunc(function(m){}) // test33 myfunc(function test34(n){}) // test34 let myobj35 = { test35 : function(o){} // test35 } let myobj36 = { test36 : function _test36(p){} // test36 } var myobj37 = { test37 : function(q){} // test37 } var myobj38 = { test38 : function _test38(r){} // test38 } test39 = () => {} // test39 test40 = v => {} // test40 test41 = (w) => {} // test41 test42 = (x,y) => {} // test42 let test43 = v => {} // test43 var myobj44 = {test44 : (w) => {}} // test44 const myobj45 = { test45 : (x,y) => {} // test45 } myfunc(() => {}) // test46 myfunc(v => {}) // test47 function test48(){} // test48 function test49(s){} // test49 function test50(t,u){} // test50` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", i) } }

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 Golang, please visit: https://golang.org/pkg/regexp/