How to check if character is a letter in Javascript

Question

I am extracting a character in a Javascript string with   var first   str charAt 0     and I would like to check whether it is a letter  Strangely  it does not seem like such functionality exists in Javascript  At least I cannot find it   How can I test this

User · Answer

It s possible to know if the character is a letter or not by using a standard builtin function isNaN or Number isNaN   from ES6   isNaN  s      true isNaN  -      true isNaN  32      false   32  is converted to the number 32 which is not NaN   It retruns true if the given value is not a number  otherwise false

User · Answer

We can check also in simple way as     x000D   x000D  function isLetter char   x000D      return    char  gt    A   amp  amp   char  lt    Z      x000D                char  gt    a   amp  amp   char  lt    z      x000D    x000D   x000D   x000D  console log isLetter  a     x000D  console log isLetter 3    x000D  console log isLetter  H     x000D   x000D   x000D

User · Answer

I m posting here because I didn t want to post a new question  Assuming there aren t any single character declarations in the code  you can eval   the character to cause an error and check the type of the character  Something like    x000D   x000D  function testForLetter character    x000D    try   x000D        Variable declarations can t start with digits or operators x000D        If no error is thrown check for dollar or underscore  Those are the only nonletter characters that are allowed as identifiers x000D      eval  let     character         x000D      let regExSpecial             x000D      return regExSpecial test character   x000D      catch  error    x000D      return false  x000D      x000D    x000D   x000D  console log testForLetter          returns false  x000D  console log testForLetter  5       returns false  x000D  console log testForLetter          returns true  x000D  console log testForLetter          returns false  x000D   x000D   x000D

User · Answer

This solution works with special characters too  for instance                         2 steps    Remove the accents  based on this answer  Remove accents diacritics in a string in JavaScript Check if a to z character  using regex or unicode  your choice    Live demos of my solution    using global functions using javascript module pattern   Note  I posted the solution that uses global functions as it s probably the simplest to understand  But do look into  javascript module pattern  if you want better code  cleaner  easier to maintain and extend   see impressivewebs com my-current-javascript-design-pattern and also this YouTube video  presentation by Paul Irish     x000D   x000D  var defaultDiacriticsRemovalap     x000D        base   A    letters    u0041 u24B6 uFF21 u00C0 u00C1 u00C2 u1EA6 u1EA4 u1EAA u1EA8 u00C3 u0100 u0102 u1EB0 u1EAE u1EB4 u1EB2 u0226 u01E0 u00C4 u01DE u1EA2 u00C5 u01FA u01CD u0200 u0202 u1EA0 u1EAC u1EB6 u1E00 u0104 u023A u2C6F    x000D        base   AA   letters    uA732    x000D        base   AE   letters    u00C6 u01FC u01E2    x000D        base   AO   letters    uA734    x000D        base   AU   letters    uA736    x000D        base   AV   letters    uA738 uA73A    x000D        base   AY   letters    uA73C    x000D        base   B    letters    u0042 u24B7 uFF22 u1E02 u1E04 u1E06 u0243 u0182 u0181    x000D        base   C    letters    u0043 u24B8 uFF23 u0106 u0108 u010A u010C u00C7 u1E08 u0187 u023B uA73E    x000D        base   D    letters    u0044 u24B9 uFF24 u1E0A u010E u1E0C u1E10 u1E12 u1E0E u0110 u018B u018A u0189 uA779    x000D        base   DZ   letters    u01F1 u01C4    x000D        base   Dz   letters    u01F2 u01C5    x000D        base   E    letters    u0045 u24BA uFF25 u00C8 u00C9 u00CA u1EC0 u1EBE u1EC4 u1EC2 u1EBC u0112 u1E14 u1E16 u0114 u0116 u00CB u1EBA u011A u0204 u0206 u1EB8 u1EC6 u0228 u1E1C u0118 u1E18 u1E1A u0190 u018E    x000D        base   F    letters    u0046 u24BB uFF26 u1E1E u0191 uA77B    x000D        base   G    letters    u0047 u24BC uFF27 u01F4 u011C u1E20 u011E u0120 u01E6 u0122 u01E4 u0193 uA7A0 uA77D uA77E    x000D        base   H    letters    u0048 u24BD uFF28 u0124 u1E22 u1E26 u021E u1E24 u1E28 u1E2A u0126 u2C67 u2C75 uA78D    x000D        base   I    letters    u0049 u24BE uFF29 u00CC u00CD u00CE u0128 u012A u012C u0130 u00CF u1E2E u1EC8 u01CF u0208 u020A u1ECA u012E u1E2C u0197    x000D        base   J    letters    u004A u24BF uFF2A u0134 u0248    x000D        base   K    letters    u004B u24C0 uFF2B u1E30 u01E8 u1E32 u0136 u1E34 u0198 u2C69 uA740 uA742 uA744 uA7A2    x000D        base   L    letters    u004C u24C1 uFF2C u013F u0139 u013D u1E36 u1E38 u013B u1E3C u1E3A u0141 u023D u2C62 u2C60 uA748 uA746 uA780    x000D        base   LJ   letters    u01C7    x000D        base   Lj   letters    u01C8    x000D        base   M    letters    u004D u24C2 uFF2D u1E3E u1E40 u1E42 u2C6E u019C    x000D        base   N    letters    u004E u24C3 uFF2E u01F8 u0143 u00D1 u1E44 u0147 u1E46 u0145 u1E4A u1E48 u0220 u019D uA790 uA7A4    x000D        base   NJ   letters    u01CA    x000D        base   Nj   letters    u01CB    x000D        base   O    letters    u004F u24C4 uFF2F u00D2 u00D3 u00D4 u1ED2 u1ED0 u1ED6 u1ED4 u00D5 u1E4C u022C u1E4E u014C u1E50 u1E52 u014E u022E u0230 u00D6 u022A u1ECE u0150 u01D1 u020C u020E u01A0 u1EDC u1EDA u1EE0 u1EDE u1EE2 u1ECC u1ED8 u01EA u01EC u00D8 u01FE u0186 u019F uA74A uA74C    x000D        base   OI   letters    u01A2    x000D        base   OO   letters    uA74E    x000D        base   OU   letters    u0222    x000D        base   OE   letters    u008C u0152    x000D        base   oe   letters    u009C u0153    x000D        base   P    letters    u0050 u24C5 uFF30 u1E54 u1E56 u01A4 u2C63 uA750 uA752 uA754    x000D        base   Q    letters    u0051 u24C6 uFF31 uA756 uA758 u024A    x000D        base   R    letters    u0052 u24C7 uFF32 u0154 u1E58 u0158 u0210 u0212 u1E5A u1E5C u0156 u1E5E u024C u2C64 uA75A uA7A6 uA782    x000D        base   S    letters    u0053 u24C8 uFF33 u1E9E u015A u1E64 u015C u1E60 u0160 u1E66 u1E62 u1E68 u0218 u015E u2C7E uA7A8 uA784    x000D        base   T    letters    u0054 u24C9 uFF34 u1E6A u0164 u1E6C u021A u0162 u1E70 u1E6E u0166 u01AC u01AE u023E uA786    x000D        base   TZ   letters    uA728    x000D        base   U    letters    u0055 u24CA uFF35 u00D9 u00DA u00DB u0168 u1E78 u016A u1E7A u016C u00DC u01DB u01D7 u01D5 u01D9 u1EE6 u016E u0170 u01D3 u0214 u0216 u01AF u1EEA u1EE8 u1EEE u1EEC u1EF0 u1EE4 u1E72 u0172 u1E76 u1E74 u0244    x000D        base   V    letters    u0056 u24CB uFF36 u1E7C u1E7E u01B2 uA75E u0245    x000D        base   VY   letters    uA760    x000D        base   W    letters    u0057 u24CC uFF37 u1E80 u1E82 u0174 u1E86 u1E84 u1E88 u2C72    x000D        base   X    letters    u0058 u24CD uFF38 u1E8A u1E8C    x000D        base   Y    letters    u0059 u24CE uFF39 u1EF2 u00DD u0176 u1EF8 u0232 u1E8E u0178 u1EF6 u1EF4 u01B3 u024E u1EFE    x000D        base   Z    letters    u005A u24CF uFF3A u0179 u1E90 u017B u017D u1E92 u1E94 u01B5 u0224 u2C7F u2C6B uA762    x000D        base   a    letters    u0061 u24D0 uFF41 u1E9A u00E0 u00E1 u00E2 u1EA7 u1EA5 u1EAB u1EA9 u00E3 u0101 u0103 u1EB1 u1EAF u1EB5 u1EB3 u0227 u01E1 u00E4 u01DF u1EA3 u00E5 u01FB u01CE u0201 u0203 u1EA1 u1EAD u1EB7 u1E01 u0105 u2C65 u0250    x000D        base   aa   letters    uA733    x000D        base   ae   letters    u00E6 u01FD u01E3    x000D        base   ao   letters    uA735    x000D        base   au   letters    uA737    x000D        base   av   letters    uA739 uA73B    x000D        base   ay   letters    uA73D    x000D        base   b    letters    u0062 u24D1 uFF42 u1E03 u1E05 u1E07 u0180 u0183 u0253    x000D        base   c    letters    u0063 u24D2 uFF43 u0107 u0109 u010B u010D u00E7 u1E09 u0188 u023C uA73F u2184    x000D        base   d    letters    u0064 u24D3 uFF44 u1E0B u010F u1E0D u1E11 u1E13 u1E0F u0111 u018C u0256 u0257 uA77A    x000D        base   dz   letters    u01F3 u01C6    x000D        base   e    letters    u0065 u24D4 uFF45 u00E8 u00E9 u00EA u1EC1 u1EBF u1EC5 u1EC3 u1EBD u0113 u1E15 u1E17 u0115 u0117 u00EB u1EBB u011B u0205 u0207 u1EB9 u1EC7 u0229 u1E1D u0119 u1E19 u1E1B u0247 u025B u01DD    x000D        base   f    letters    u0066 u24D5 uFF46 u1E1F u0192 uA77C    x000D        base   g    letters    u0067 u24D6 uFF47 u01F5 u011D u1E21 u011F u0121 u01E7 u0123 u01E5 u0260 uA7A1 u1D79 uA77F    x000D        base   h    letters    u0068 u24D7 uFF48 u0125 u1E23 u1E27 u021F u1E25 u1E29 u1E2B u1E96 u0127 u2C68 u2C76 u0265    x000D        base   hv   letters    u0195    x000D        base   i    letters    u0069 u24D8 uFF49 u00EC u00ED u00EE u0129 u012B u012D u00EF u1E2F u1EC9 u01D0 u0209 u020B u1ECB u012F u1E2D u0268 u0131    x000D        base   j    letters    u006A u24D9 uFF4A u0135 u01F0 u0249    x000D        base   k    letters    u006B u24DA uFF4B u1E31 u01E9 u1E33 u0137 u1E35 u0199 u2C6A uA741 uA743 uA745 uA7A3    x000D        base   l    letters    u006C u24DB uFF4C u0140 u013A u013E u1E37 u1E39 u013C u1E3D u1E3B u017F u0142 u019A u026B u2C61 uA749 uA781 uA747    x000D        base   lj   letters    u01C9    x000D        base   m    letters    u006D u24DC uFF4D u1E3F u1E41 u1E43 u0271 u026F    x000D        base   n    letters    u006E u24DD uFF4E u01F9 u0144 u00F1 u1E45 u0148 u1E47 u0146 u1E4B u1E49 u019E u0272 u0149 uA791 uA7A5    x000D        base   nj   letters    u01CC    x000D        base   o    letters    u006F u24DE uFF4F u00F2 u00F3 u00F4 u1ED3 u1ED1 u1ED7 u1ED5 u00F5 u1E4D u022D u1E4F u014D u1E51 u1E53 u014F u022F u0231 u00F6 u022B u1ECF u0151 u01D2 u020D u020F u01A1 u1EDD u1EDB u1EE1 u1EDF u1EE3 u1ECD u1ED9 u01EB u01ED u00F8 u01FF u0254 uA74B uA74D u0275    x000D        base   oi   letters    u01A3    x000D        base   ou   letters    u0223    x000D        base   oo   letters    uA74F    x000D        base   p   letters    u0070 u24DF uFF50 u1E55 u1E57 u01A5 u1D7D uA751 uA753 uA755    x000D        base   q   letters    u0071 u24E0 uFF51 u024B uA757 uA759    x000D        base   r   letters    u0072 u24E1 uFF52 u0155 u1E59 u0159 u0211 u0213 u1E5B u1E5D u0157 u1E5F u024D u027D uA75B uA7A7 uA783    x000D        base   s   letters    u0073 u24E2 uFF53 u00DF u015B u1E65 u015D u1E61 u0161 u1E67 u1E63 u1E69 u0219 u015F u023F uA7A9 uA785 u1E9B    x000D        base   t   letters    u0074 u24E3 uFF54 u1E6B u1E97 u0165 u1E6D u021B u0163 u1E71 u1E6F u0167 u01AD u0288 u2C66 uA787    x000D        base   tz   letters    uA729    x000D        base   u   letters     u0075 u24E4 uFF55 u00F9 u00FA u00FB u0169 u1E79 u016B u1E7B u016D u00FC u01DC u01D8 u01D6 u01DA u1EE7 u016F u0171 u01D4 u0215 u0217 u01B0 u1EEB u1EE9 u1EEF u1EED u1EF1 u1EE5 u1E73 u0173 u1E77 u1E75 u0289    x000D        base   v   letters    u0076 u24E5 uFF56 u1E7D u1E7F u028B uA75F u028C    x000D        base   vy   letters    uA761    x000D        base   w   letters    u0077 u24E6 uFF57 u1E81 u1E83 u0175 u1E87 u1E85 u1E98 u1E89 u2C73    x000D        base   x   letters    u0078 u24E7 uFF58 u1E8B u1E8D    x000D        base   y   letters    u0079 u24E8 uFF59 u1EF3 u00FD u0177 u1EF9 u0233 u1E8F u00FF u1EF7 u1E99 u1EF5 u01B4 u024F u1EFF    x000D        base   z   letters    u007A u24E9 uFF5A u017A u1E91 u017C u017E u1E93 u1E95 u01B6 u0225 u0240 u2C6C uA763   x000D     x000D   x000D  var diacriticsMap       x000D  for  var i 0  i  lt  defaultDiacriticsRemovalap length  i     x000D      var letters   defaultDiacriticsRemovalap i  letters split      x000D      for  var j 0  j  lt  letters length   j     x000D          diacriticsMap letters j     defaultDiacriticsRemovalap i  base  x000D        x000D    x000D   x000D  function removeDiacriticFromChar  char    x000D      return diacriticsMap char     char   x000D    x000D   x000D   x000D     x000D       1  Remove the accent  based on answer of https   stackoverflow com questions 990904 javascript-remove-accents-in-strings x000D       2  Check if a to z character  using regex or unicode  your choice  here using regex  x000D     x000D      x000D  function isLetter char    x000D    var charWithoutAccent   removeDiacriticFromChar char        1     x000D    return charWithoutAccent match   a-z  i                     2     x000D    x000D   x000D  console log   is  u  is a letter       isLetter  u      true     false      x000D  console log   is      is a letter       isLetter          true     false      x000D  console log   is      is a letter       isLetter          true     false      x000D  console log   is      is a letter       isLetter          true     false      x000D  console log   is      is a letter       isLetter          true     false      x000D  console log   is      is a letter       isLetter          true     false      x000D  console log   is      is a letter       isLetter          true     false      x000D  console log   is      is a letter       isLetter          true     false      x000D   x000D   x000D

User · Answer

to check if the given string contain alphabets     function isPangram sentence           let lowerCased   sentence toLowerCase            let letters    abcdefghijklmnopqrstuvwxyz              traditional for loop can also be used         for  let char of letters               if   lowerCased includes char   return false                    return true

User · Answer

So we got a first character using charArt   function then try to match ir using  regular expression to check if there is an letter lowercased starting from a to z and return it results as a boolean  Boolean   Foo  charAt 0  match   a-zA-Z        false Boolean  Foo  charAt 0  match   a-zA-Z        true

User · Answer

How about using ASCII codes   let n   str charCodeAt 0   let strStartsWithALetter    n  gt   65  amp  amp  n  lt  91      n  gt   97  amp  amp  n  lt  123

User · Answer

I don t believe there is a built-in function for that   But it s easy enough to write with a regex   function isLetter str      return str length     1  amp  amp  str match   a-z  i

User · Answer

I believe this plugin has the capabilities you seek  http   xregexp com plugins   github link    https   github com slevithan xregexp   With it you can simply match all unicode letters with  p L    Read the header of this source file to see which categories it supports  http   xregexp com plugins xregexp-unicode-categories js

User · Answer

if  char toUpperCase      char toLowerCase       Will return true only in case of letter As point out in below comment  if your character is non English  High Ascii or double byte range then you need to add check for code point  if  char toUpperCase      char toLowerCase      char codePointAt 0   gt  127

User · Answer

I made a function to do this   var isLetter   function  character      if   character charCodeAt    gt   65  amp  amp  character charCodeAt    lt   90      character charCodeAt    gt   97  amp  amp  character charCodeAt    lt   122          return true        else      return false          This basically verifies in the ASCII table if the code of the character refers to a Letter   You can see the ASCII table on this link and compare columns DEC  where is the code  and symbol  https   www ascii-code com   Note  My function is true only to  simple  letters  things like                        it will return false    but if you needed you can adapt this function to de other conditions

User · Answer

ES6 supports unicode-aware regular expressions   RegExp    p L    u   test str    This works for all alphabets   Unfortunately  there is a bug in Firefox  will be fixed in version 78  that prevents this from being used universally  But if you can control your runtime environment and it supports it  e g   Node js   this is a straightforward  comprehensive solution   Atlernatively  XRegExp provides a polyfill of modern regular expression to all browsers

User · Answer

With respect to those special characters not being taken into account by simpler checks such as   a-zA-Z   test c   it can be beneficial to leverage ECMAScript case transformation  toUpperCase   It will take into account non-ASCII Unicode character classes of some foreign alphabets   function isLetter c      return c toLowerCase      c toUpperCase        NOTE  this solution will work only for most Latin  Greek  Armenian and Cyrillic scripts  It will NOT work for Chinese  Japanese  Arabic  Hebrew and most other scripts

[javascript] How to check if character is a letter in Javascript?

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