JavaScript dictionary with names

Question

I want to create a dictionary in JavaScript like the following  myMappings            quot Name quot   10           quot Phone quot   10           quot Address quot   50           quot Zip quot   10           quot Comments quot   20      I want to populate an HTML table later and want to set the titles of table to the first column of myMappings and the width of columns to the second  Is there a clean way to do it

User · Answer

An easier  native and more efficient way of emulating a dict in JavaScript than a hash table  It also exploits that JavaScript is weakly typed  Rather type inference  Here s how  an excerpt from Google Chrome s console   var myDict        myDict one   1  1  myDict two   2  2  if  myDict hasOwnProperty  three        console log myDict two     else     console log  Key does not exist       Key does not exist  VM361 8  if  myDict hasOwnProperty  two        console log myDict two     else     console log  Key does not exist       2 VM362 4  Object keys myDict     quot one quot    quot two quot    delete myDict two   true  myDict hasOwnProperty  two    false  myDict two undefined  myDict one 1

User · Answer

Another approach would be to have an array of objects  with each individual object holding the properties of a column  This slightly changes the structure of  myMappings   but makes it easy to work with   var myMappings           title   Name   width   10            title   Phone   width   10            title   Address   width   50            title   Zip   width   10            title   Comments   width   20          Then you could easily iterate through all your  columns  with a for loop   for  var i   0  i  lt  myMappings length  i    1           myMappings i  title            myMappings i  width

User · Answer

You may be trying to use a JSON object  var myMappings      quot name quot    quot 10  quot    quot phone quot    quot 10  quot    quot address quot    quot 50  quot   etc      To access  myMappings name  myMappings phone  etc

User · Answer

The main problem I see with what you have is that it s difficult to loop through  for populating a table   Simply use an array of arrays   var myMappings           Name    10        Note the quotes around  10         Phone    10            etc            which simplifies access   myMappings 0  0      column name myMappings 0  1      column width     Alternatively   var myMappings         names    Name    Phone   etc          widths    10     10    etc          And access with   myMappings names 0   myMappings widths 0

User · Answer

Try  var myMappings          quot Name quot        quot 10  quot        quot Phone quot       quot 10  quot        quot Address quot     quot 50  quot        quot Zip quot         quot 10  quot        quot Comments quot    quot 20  quot        Access is like this myMappings  quot Name quot      Returns  quot 10  quot  myMappings Name    The same thing as above     To loop through    for var title in myMappings           Do whatever with myMappings title

User · Answer

An object technically is a dictionary  var myMappings         mykey1   myValue       mykey2   myValue      var myVal   myMappings  myKey1     alert myVal      myValue  You can even loop through one  for var key in myMappings        var myVal   myMappings key       alert myVal      There is no reason whatsoever to reinvent the wheel  And of course  assignment goes like  myMappings  mykey3      my value    And ContainsKey  if  myMappings hasOwnProperty  myKey3          alert  key already exists        I suggest you follow this  http   javascriptissexy com how-to-learn-javascript-properly

User · Answer

I suggest not using an array unless you have multiple objects to consider  There isn t anything wrong this statement  var myMappings          quot Name quot   0 1       quot Phone quot   0 1       quot Address quot   0 5       quot Zip quot   0 1       quot Comments quot   0 2     for  var col in myMappings        alert  myMappings col    100     quot   quot

User · Answer

Here s a dictionary that will take any type of key as long as the toString   property returns unique values  The dictionary uses anything as the value for the key value pair  See Would JavaScript Benefit from a Dictionary Object  To use the dictionary as is  var dictFact   new Dict    var myDict   dictFact New    myDict addOrUpdate  quot key1 quot    quot Value1 quot    myDict addOrUpdate  quot key2 quot    quot Value2 quot    myDict addOrUpdate  quot keyN quot    quot ValueN quot     The dictionary code is below       Dictionary Factory Object   Holds common object functions  similar to V-Table   this New   used to create new dictionary objects   Uses Object defineProperties so won t work on older browsers    Browser Compatibility  https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Object defineProperties         Firefox  Gecko  4 0  2   Chrome 5  Internet Explorer 9  Opera 11 60  Safari 5    function Dict                   Create a new Dictionary            this New   function              return new dict                         Return argument f if it is a function otherwise return undefined            function ensureF f            if  isFunct f                 return f                       function isFunct f            return  typeof f     quot function quot                        Add a  quot   quot  as first character just to be sure valid property name            function makeKey k            return  quot   quot    k                       Key Value Pair object - held in array            function newkvp key  value            return               key  key              value  value              toString  function      return this key                 valueOf  function      return this key                                    Return the current set of keys             function keys a               remove the leading  quot - quot  character from the keys         return a map function  e    return e key substr 1                  Alternative  Requires Opera 12 vs  11 60            -- Must pass the internal object instead of the array            -- Still need to remove the leading  quot - quot  to return user key values               Object keys o  map function  e    return e key substr 1                            Return the current set of values             function values a            return a map function e    return e value                            Return the current set of key value pairs             function kvPs a               Remove the leading  quot - quot  character from the keys         return a map function  e    return newkvp e key substr 1   e value                           Returns true if key exists in the dictionary        k - Key to check  with the leading  quot   quot  character             function exists k  o            return o hasOwnProperty k                       Array Map implementation            function map a  f            if   isFunct f     return            return a map function  e  i    return f e value  i                           Array Every implementation            function every a  f            if   isFunct f     return            return a every function  e  i    return f e value  i                          Returns subset of  quot values quot  where function  quot f quot  returns true for the  quot value quot             function filter a  f            if   isFunct f    return            var ret   a filter function  e  i    return f e value  i                  if anything returned by array filter  then get the  quot values quot  from the key value pairs         if  ret  amp  amp  ret length  gt  0                ret   values ret                     return ret                      Array Reverse implementation            function reverse a  o            a reverse            reindex a  o  0                        Randomize array element order in-place        Using Fisher-Yates shuffle algorithm             function shuffle a  o            var j  t          for  var i   a length - 1  i  gt  0  i--                j   Math floor Math random      i   1                t   a i               a i    a j               a j    t                    reindex a  o  0           return a                     Array Some implementation            function some a  f            if   isFunct f     return            return a some function  e  i    return f e value  i                          Sort the dictionary  Sorts the array and reindexes the object        a - dictionary array       o - dictionary object       sf - dictionary default sort function  can be undefined        f - sort method sort function argument  can be undefined             function sort a  o  sf  f            var sf1   f    sf     sort function  method used if not undefined            if there is a customer sort function  use it         if  isFunct sf1                 a sort function  e1  e2    return sf1 e1 value  e2 value                         else                  sort by key values             a sort                         reindex - adds O n  to perf         reindex a  o  0              return sorted values  not entire array             adds O n  to perf         return values a                        forEach iteration of  quot values quot          uses  quot for quot  loop to allow exiting iteration when function returns true            function forEach a  f            if   isFunct f     return               use for loop to allow exiting early and not iterating all items         for var i   0  i  lt  a length  i                  if  f a i  value  i     break                                   forEachR iteration of  quot values quot  in reverse order         uses  quot for quot  loop to allow exiting iteration when function returns true            function forEachR a  f            if   isFunct f     return               use for loop to allow exiting early and not iterating all items         for  var i   a length - 1  i  gt  -1  i--                if  f a i  value  i     break                                  Add a new Key Value Pair  or update the value of an existing key value pair            function add key  value  a  o  resort  sf            var k   makeKey key              Update value if key exists         if  exists k  o                 a o k   value   value                    else                  Add a new Key value Pair             var kvp   newkvp k  value               o kvp key    a length              a push kvp                        resort if requested         if  resort    sort a  o  sf                          Removes an existing key value pair and returns the  quot value quot  If the key does not exists  returns undefined            function remove key  a  o            var k   makeKey key              return undefined if the key does not exist         if   exists k  o     return               get the array index         var i   o k              get the key value pair         var ret   a i              remove the array element         a splice i  1              remove the object property         delete o k              reindex the object properties from the remove element to end of the array         reindex a  o  i              return the removed value         return ret value                       Returns true if key exists in the dictionary        k - Key to check  without the leading  quot   quot  character             function keyExists k  o            return exists makeKey k   o                        Returns value assocated with  quot key quot   Returns undefined if key not found            function item key  a  o            var k   makeKey key           if  exists k  o                 return a o k   value                                changes index values held by object properties to match the array index location       Called after sorting or removing            function reindex a  o  i           for  var j   i  j  lt  a length  j                  o a j  key    j                                The  quot real dictionary quot             function dict             var  a               var  o               var  sortF           Object defineProperties this                 quot length quot     get  function      return  a length     enumerable  true                 quot keys quot     get  function     return keys  a      enumerable  true                 quot values quot     get  function     return values  a      enumerable  true                 quot keyValuePairs quot     get  function     return kvPs  a      enumerable  true                quot sortFunction quot     get  function     return  sortF     set  function funct     sortF   ensureF funct      enumerable  true                           Array Methods - Only modification to not pass the actual array to the callback function         this map   function funct    return map  a  funct              this every   function funct    return every  a  funct              this filter   function funct    return filter  a  funct              this reverse   function     reverse  a   o              this shuffle   function      return shuffle  a   o              this some   function funct    return some  a  funct              this sort   function funct    return sort  a   o   sortF  funct                  Array Methods - Modified aborts when funct returns true          this forEach   function  funct    forEach  a  funct                 forEach in reverse order         this forEachRev   function  funct    forEachR  a  funct                 Dictionary Methods         this addOrUpdate   function key  value  resort    return add key  value   a   o  resort   sortF              this remove   function key    return remove key   a   o              this exists   function key    return keyExists key   o              this item   function key    return item key   a   o              this get   function  index    if  index  gt  -1  amp  amp  index  lt   a length    return  a index  value                this clear   function      a        o                   return this             return this

[javascript] JavaScript dictionary with names

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