Iterate over object keys in node js

Question

Since Javascript 1 7 there is an Iterator object  which allows this   var a  a 1 b 2 c 3   var it Iterator a    function iterate        try             console log it next             setTimeout iterate 1000        catch  err if err instanceof StopIteration              console log  End of record  n            catch  err              console log  Unknown error      err description     n                 iterate      is there something like this in node js    Right now i m using   function Iterator o         var k         for var i in o           k push i               var k Object keys o       return           next function                return k shift                         but that produces a lot of overhead by storing all the object keys in k

User · Answer

Also remember that you can pass a second argument to the  forEach   function specifying the object to use as the this keyword      myOjbect is the object you want to iterate     Notice the second argument  secondArg  we passed to  forEach  Object keys myObject  forEach function element  key   array         element is the name of the key       key is just a numerical value for the array       array is the array of all the keys       this keyword   secondArg   this foo    this bar       secondArg

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adjust his code   Object prototype each   function iterateFunc            var counter   0  keys   Object keys this   currentKey  len   keys length          var that   this          var next   function                  if  counter  lt  len                    currentKey   keys counter                     iterateFunc currentKey  that currentKey                     next                  else                   that   counter   keys   currentKey   len   next   undefined                                   next                   property1   sdsfs   property2   chat     each function key  val               do things         console log key

User · Answer

I m new to node js  about 2 weeks   but I ve just created a module that recursively reports to the console the contents of an object   It will list all or search for a specific item and then drill down by a given depth if need be   Perhaps you can customize this to fit your needs   Keep It Simple   Why complicate       use strict      console log  START  AFutils        Recusive console output report of an Object    Use this as AFutils reportObject req      1  3      To list all items in req object by 3 levels    Use this as AFutils reportObject req   headers   1  10      To find  headers  item and then list by 10 levels    yes  I m OLD School   I like to see the scope start AND end      -P exports reportObject   function obj  key  level  deep         if   obj                 return             var nextLevel   level   1       var keys  typer  prop      if key                   requested field         keys   key split      join     split                 else            do for all         keys   Object keys obj             var len   keys length      var add           for var j   1  j  lt  level  j                     I would normally do  add   add substr 0  level   of a precreated multi-tab  add  string here  but Sublime keeps replacing with spaces  even with the   translate tabs to spaces   false  setting     angry          add      t              for  var i   0  i  lt  len  i                   prop   obj keys i            if  prop                           Don t show   waste of space in console window                  console log add   level      UNDEFINED      keys i                            else                       typer   typeof prop               if typer     function                                    Don t bother showing fundtion code                    console log add   level           keys i              typer                                   else             if typer     object                                 console log add   level           keys i              typer                         if nextLevel  lt   deep                                           drop the key search mechanism if first level item has been found                        this reportObject prop      nextLevel  deep      Recurse into                                             else                                  Basic report                 console log add   level           keys i              typer            prop                                           return         console log  END  AFutils

User · Answer

What you want is lazy iteration over an object or array  This is not possible in ES5  thus not possible in node js   We will get this eventually   The only solution is finding a node module that extends V8 to implement iterators  and probably generators   I couldn t find any implementation  You can look at the spidermonkey source code and try writing it in C   as a V8 extension   You could try the following  however it will also load all the keys into memory  Object keys o  forEach function key      var val   o key     logic          However since Object keys is a native method it may allow for better optimisation   Benchmark  As you can see Object keys is significantly faster  Whether the actual memory storage is more optimum is a different matter   var async       async forEach   function o  cb      var counter   0      keys   Object keys o       len   keys length    var next   function         if  counter  lt  len  cb o keys counter      next          next        async forEach obj  function val  next         do things   setTimeout next  100

User · Answer

For simple iteration of key values  sometimes libraries like underscorejs can be your friend   const     require  underscore       each a  function  value  key           handle       just for reference

[javascript] Iterate over object keys in node.js

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