Write objects into file with Node js

Question

I ve searched all over stackoverflow   google for this  but can t seem to figure it out    I m scraping social media links of a given URL page  and the function returns an object with a list of URLs    When I try to write this data into a different file  it outputs to the file as  object Object  instead of the expected          https   twitter com    101Cookbooks        http   www facebook com 101cookbooks    as it does when I console log   the results   This is my sad attempt to read and write a file in Node  trying to read each line the url  and input through a function call request line  gotHTML     fs readFileSync    urls txt   toString   split   n   forEach function  line       console log line        var obj   request line  gotHTML        console log obj        fs writeFileSync    data json   obj    utf-8              for reference -- the gotHTML function    function gotHTML err  resp  html        var social ids             if err           return console log err          else if  resp statusCode     200            var parsedHTML     load html             parsedHTML  a   map function i  link               var href     link  attr  href                for var i 0  i lt socialurls length  i                     if socialurls i  test href   amp  amp  social ids indexOf href   lt  0                         social ids push href                                                               return social ids

User · Accepted Answer

obj is an array in your example     fs writeFileSync filename  data   options   requires either String or Buffer in the data parameter  see docs   Try to write the array in a string format      writes  https   twitter com    101Cookbooks    http   www facebook com 101cookbooks  fs writeFileSync    data json   obj join         utf-8       Or      writes   https   twitter com    101Cookbooks    http   www facebook com 101cookbooks   var util   require  util    fs writeFileSync    data json   util inspect obj     utf-8      edit  The reason you see the array in your example is because node s implementation of console log doesn t just call toString  it calls util format see console js source

User · Answer

If you re geting  object object  then use JSON stringify  fs writeFile    data json   JSON stringify obj     utf-8     It worked for me

User · Answer

In my experience JSON stringify is slightly faster than util inspect  I had to save the result object of a DB2 query as a json file  The query returned an object of 92k rows  the conversion took very long to complete with util inspect  so I did the following test by writing the same 1000 record object to a file with both methods    JSON Stringify  fs writeFile    data json   JSON stringify obj  null  2       Time  3 57  3 min 57 sec   Result s format              PROB    00001        BO    AXZ        CNTRY    649                   util inspect  var util   require  util    fs writeFile    data json   util inspect obj  false  2  false       Time  4 12  4 min 12 sec   Result s format       PROB   00001       BO   AXZ       CNTRY   649

User · Answer

Building on what deb2fast said I would also pass in a couple of extra parameters to JSON stringify   to get it to pretty format   fs writeFileSync    data json   JSON stringify obj  null  2     utf-8      The second param is an optional replacer function which you don t need in this case so null works   The third param is the number of spaces to use for indentation  2 and 4 seem to be popular choices

User · Answer

Just incase anyone else stumbles across this  I use the fs-extra library in node and write javascript objects to a file like this   const fse   require  fs-extra    fse outputJsonSync  path to output file json   objectToWriteToFile

User · Answer

could you try doing JSON stringify obj    Like this   var stringify   JSON stringify obj   fs writeFileSync    data json   stringify    utf-8

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