How to convert characters to HTML entities using plain JavaScript

Question

I have the following   var text      bergro  e   pfel mit W  rmern     I m searching for a Javascript function to transform the text so that every special letter is represented by its HTML entity sequence like this   var newText   magicFunction text       newText     amp Uuml bergro amp szlig e  amp Auml pfel mit W amp uuml rmern     The function should not only escape the letters of this example but also all of these   How would you achieve that  Is there any existing function out there   Plain  because a solution without a framework is preferred   Btw  Yes  I ve seen this question but it doesn t address my need

User · Answer

I adapted one of the answers from the referenced question  but added the ability to define an explicit mapping for character names   var char names         160  nbsp       161  iexcl       220  Uuml       223  szlig       196  Auml       252  uuml           function HTMLEncode str        var aStr   str split               i   aStr length           aRet             while  --i  gt   0          var iC   aStr i  charCodeAt           if  iC  lt  32     iC  gt  32  amp  amp  iC  lt  65     iC  gt  127     iC gt 90  amp  amp  iC lt 97             if char names iC   undefined             aRet push   amp   char names iC                          else            aRet push   amp    iC                          else           aRet push aStr i                       return aRet reverse   join            var text      bergro  e   pfel mit W  rmer    alert HTMLEncode text

User · Answer

Having a lookup table with a bazillion replace   calls is slow and not maintainable   Fortunately  the build-in escape   function also encodes most of the same characters  and puts them in a consistent format   XX  where XX is the hex value of the character    So  you can let escape   method do most of the work for you and just change its answer to be HTML entities instead of URL-escaped characters   htmlescaped   escape mystring  replace        g   amp  x 1       This uses the hex format for escaping values rather than the named entities  but for storing and displaying the values  it works just as well as named entities   Of course  escape also escapes characters you don t need to escape in HTML  spaces  for instance   but you can unescape them with a few replace calls   Edit  I like bucabay s answer better than my own    handles a larger range of characters  and requires no hacking afterward to get spaces  slashes  etc  unescaped

User · Answer

The he library is the only 100  reliable solution that I know of  He is written by Mathias Bynens - one of the world s most renowned JavaScript gurus - and has the following features    Support for all standardized named character references Support for unicode Works fine with ambiguous ampersands   Example use he encode  foo    bar   baz  qux        Output    foo  amp  xA9  bar  amp  x2260  baz  amp  x1D306  qux   he decode  foo  amp copy  bar  amp ne  baz  amp  x1D306  qux       Output    foo    bar   baz  qux

User · Answer

Demo on JSFiddle  here s a tiny stand alone method that     attempts to consolidate the answers on this page  without using a library works in older browsers supports surrogate pairs  like emojis  applies character overrides  what s that  not sure exactly    i don t know too much about unicode  but it seems to be working well       escape a string for display in html    see also      polyfill for String prototype codePointAt      https   raw githubusercontent com mathiasbynens String prototype codePointAt master codepointat js    how to convert characters to html entities        http   stackoverflow com a 1354491 347508    html overrides from       https   html spec whatwg org multipage syntax html table-charref-overrides   http   stackoverflow com questions 1354064 how-to-convert-characters-to-html-entities-using-plain-javascript 23831239 comment36668052 1354098  var  escape overrides     0x00   uFFFD  0x80   u20AC  0x82   u201A  0x83   u0192  0x84   u201E  0x85   u2026  0x86   u2020  0x87   u2021  0x88   u02C6  0x89   u2030  0x8A   u0160  0x8B   u2039  0x8C   u0152  0x8E   u017D  0x91   u2018  0x92   u2019  0x93   u201C  0x94   u201D  0x95   u2022  0x96   u2013  0x97   u2014  0x98   u02DC  0x99   u2122  0x9A   u0161  0x9B   u203A  0x9C   u0153  0x9E   u017E  0x9F   u0178       function escapeHtml str       return str replace     u0000- uD799    uD800- uDBFF   uDC00- uFFFF   g  function c            var c1   c charCodeAt 0              ascii character  use override or escape         if  c1  lt   0xFF   return  c1  escape overrides c1   c1 escape c  replace        g   amp  x 1                utf8 16 character         else if  c length    1   return   amp      c1                    surrogate pair         else if  c length    2  amp  amp  c1  gt   0xD800  amp  amp  c1  lt   0xDBFF   return   amp        c1-0xD800  0x400   c charCodeAt 1  - 0xDC00   0x10000                   no clue             else return

User · Answer

I recommend to use the JS library entities  Using the library is quite simple  See the examples from docs   const entities   require  entities      encoding entities escape   amp  38          amp  x26  38   entities encodeXML   amp  38          amp amp  38   entities encodeHTML   amp  38          amp amp  amp num 38 amp semi     decoding entities decodeXML  asdf  amp amp   amp  xFF   amp  xFC   amp apos         asdf  amp           entities decodeHTML  asdf  amp amp   amp yuml   amp uuml   amp apos         asdf  amp

User · Answer

All the other solutions suggested here  as well as most other JavaScript libraries that do HTML entity encoding decoding  make several mistakes   They don   t implement the full list of named character references that browsers support  For example  htmlDecode   amp PrecedesSlantEqual    should return      i e    u227C    They don   t support encoding astral symbols correctly  For example  htmlEncode     should return something like  amp  x1D306  or  amp  119558   If an implementation returns two separate entities instead  e g   amp  xD834  amp  xDF06  or  amp  55348  amp  57094    it is broken  They don   t support decoding astral symbols correctly  htmlDecode   amp  x1D306    should return    and not      i e    uD306    They don   t implement the character reference overrides table listed in the HTML Standard  For example  htmlDecode   amp  x80    should return        i e    u20AC    They should perform decoding in a single pass  For example  htmlDecode   amp  x26 amp    should return   amp amp    not  amp    For a robust solution that avoids all these issues  use a library I wrote called he for this  From its README   he  for    HTML entities     is a robust HTML entity encoder decoder written in JavaScript  It supports all standardized named character references as per HTML  handles ambiguous ampersands and other edge cases just like a browser would  has an extensive test suite  and     contrary to many other JavaScript solutions     he handles astral Unicode symbols just fine  An online demo is available

User · Answer

Just reposting  bucababy s answer as a  bookmarklet   as it s sometimes easier than using those lookup pages   alert prompt  Enter characters to htmlEncode       replace    u00A0- u2666  g  function c       return   amp    c charCodeAt 0

User · Answer

Using escape   should work with the character code range 0x00 to 0xFF  UTF-8 range    If you go beyond 0xFF  255   such as 0x100  256  then escape   will not work   escape   u0100        u0100   and   text     u0100      A html   escape text  replace        g   amp  x 1         amp  xu0 100   So  if you want to cover all Unicode charachacters as defined on http   www w3 org TR html4 sgml entities html   then you could use something like   var html   text replace    u00A0- u00FF  g  function c       return   amp    c charCodeAt 0             Note here the range is between   u00A0- u00FF    Thats the first character code range defined in http   www w3 org TR html4 sgml entities html which is the same as what escape   covers    You ll need to add the other ranges you want to cover as well  or all of them    Example  UTF-8 range with general punctuations   u00A0- u00FF and  u2022- u2135   var html   text replace    u00A0- u00FF u2022- u2135  g  function c       return   amp    c charCodeAt 0             Edit   BTW   u00A0- u2666 should convert every Unicode character code not within ASCII range to HTML entities blindly   var html   text replace    u00A0- u2666  g  function c       return   amp    c charCodeAt 0

User · Answer

Best solution is posted at phpjs org implementation of PHP function htmlentities  The format is htmlentities string  quote style  charset  double encode  Full documentation on the PHP function which is identical can be read here

User · Answer

I fixed my problem by using encodeURIComponent   instead of escape     This might be the fix for you if the problem happens when sending your string in a URL   Try this with the phrase   hi  amp           escape   returns   hi 20 26 20 25 20 u2018    Notice the  u2018 isn t very url friendly and can break the rest of the query string   encodeURI   returns   hi 20 amp  20 25 20 E2 80 98    Notice the ampersand is still there   encodeURIComponent   returns   hi 20 26 20 25 20 E2 80 98    Finally  all of our characters are properly encoded

User · Answer

You can use   function encodeHTML str    var aStr   str split           i   aStr length       aRet           while  i--        var iC   aStr i  charCodeAt        if  iC  lt  65    iC  gt  127     iC gt 90  amp  amp  iC lt 97           aRet push   amp    iC             else         aRet push aStr i               return aRet reverse   join          This function HTMLEncodes everything that is not a-z A-Z    Edit  A rather old answer  Let s add a simpler String extension to encode all extended characters   String prototype encodeHTML   function        return this replace    u0080- u024F  g             function  v   return   amp    v charCodeAt                          usage log    bergro  e   pfel mit W  rmern  encodeHTML         gt    amp  220 bergro amp  223 e  amp  196 pfel mit W amp  252 rmern

User · Answer

With the help of bucabay and the advice to create my own function i created this one which works for me  What do you guys think  is there a better solution somewhere   if typeof escapeHtmlEntities     undefined             escapeHtmlEntities   function  text                return text replace    u00A0- u2666 lt  gt   amp   g  function c                    return   amp                       escapeHtmlEntities entityTable c charCodeAt 0          c charCodeAt 0                                                 all HTML4 entities as defined here  http   www w3 org TR html4 sgml entities html            added  amp  lt  gt  quot and apos         escapeHtmlEntities entityTable                 34    quot                38    amp                39    apos                60    lt                62    gt                160    nbsp                161    iexcl                162    cent                163    pound                164    curren                165    yen                166    brvbar                167    sect                168    uml                169    copy                170    ordf                171    laquo                172    not                173    shy                174    reg                175    macr                176    deg                177    plusmn                178    sup2                179    sup3                180    acute                181    micro                182    para                183    middot                184    cedil                185    sup1                186    ordm                187    raquo                188    frac14                189    frac12                190    frac34                191    iquest                192    Agrave                193    Aacute                194    Acirc                195    Atilde                196    Auml                197    Aring                198    AElig                199    Ccedil                200    Egrave                201    Eacute                202    Ecirc                203    Euml                204    Igrave                205    Iacute                206    Icirc                207    Iuml                208    ETH                209    Ntilde                210    Ograve                211    Oacute                212    Ocirc                213    Otilde                214    Ouml                215    times                216    Oslash                217    Ugrave                218    Uacute                219    Ucirc                220    Uuml                221    Yacute                222    THORN                223    szlig                224    agrave                225    aacute                226    acirc                227    atilde                228    auml                229    aring                230    aelig                231    ccedil                232    egrave                233    eacute                234    ecirc                235    euml                236    igrave                237    iacute                238    icirc                239    iuml                240    eth                241    ntilde                242    ograve                243    oacute                244    ocirc                245    otilde                246    ouml                247    divide                248    oslash                249    ugrave                250    uacute                251    ucirc                252    uuml                253    yacute                254    thorn                255    yuml                402    fnof                913    Alpha                914    Beta                915    Gamma                916    Delta                917    Epsilon                918    Zeta                919    Eta                920    Theta                921    Iota                922    Kappa                923    Lambda                924    Mu                925    Nu                926    Xi                927    Omicron                928    Pi                929    Rho                931    Sigma                932    Tau                933    Upsilon                934    Phi                935    Chi                936    Psi                937    Omega                945    alpha                946    beta                947    gamma                948    delta                949    epsilon                950    zeta                951    eta                952    theta                953    iota                954    kappa                955    lambda                956    mu                957    nu                958    xi                959    omicron                960    pi                961    rho                962    sigmaf                963    sigma                964    tau                965    upsilon                966    phi                967    chi                968    psi                969    omega                977    thetasym                978    upsih                982    piv                8226    bull                8230    hellip                8242    prime                8243    Prime                8254    oline                8260    frasl                8472    weierp                8465    image                8476    real                8482    trade                8501    alefsym                8592    larr                8593    uarr                8594    rarr                8595    darr                8596    harr                8629    crarr                8656    lArr                8657    uArr                8658    rArr                8659    dArr                8660    hArr                8704    forall                8706    part                8707    exist                8709    empty                8711    nabla                8712    isin                8713    notin                8715    ni                8719    prod                8721    sum                8722    minus                8727    lowast                8730    radic                8733    prop                8734    infin                8736    ang                8743    and                8744    or                8745    cap                8746    cup                8747    int                8756    there4                8764    sim                8773    cong                8776    asymp                8800    ne                8801    equiv                8804    le                8805    ge                8834    sub                8835    sup                8836    nsub                8838    sube                8839    supe                8853    oplus                8855    otimes                8869    perp                8901    sdot                8968    lceil                8969    rceil                8970    lfloor                8971    rfloor                9001    lang                9002    rang                9674    loz                9824    spades                9827    clubs                9829    hearts                9830    diams                338    OElig                339    oelig                352    Scaron                353    scaron                376    Yuml                710    circ                732    tilde                8194    ensp                8195    emsp                8201    thinsp                8204    zwnj                8205    zwj                8206    lrm                8207    rlm                8211    ndash                8212    mdash                8216    lsquo                8217    rsquo                8218    sbquo                8220    ldquo                8221    rdquo                8222    bdquo                8224    dagger                8225    Dagger                8240    permil                8249    lsaquo                8250    rsaquo                8364    euro                     usage example   var text      bergro  e   pfel mit W  rmern   alert escapeHtmlEntities  text      result    amp Uuml bergro amp szlig e  amp Auml pfel mit W amp uuml rmern    Update1  Thanks bucabay again for the    - hint Update2  Updated entity table with amp lt gt apos quot  thanks richardtallent for the hint Update3 in 2014   Mathias Bynens created a lib called  he   maybe it serves your need

[javascript] How to convert characters to HTML entities using plain JavaScript

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