Hristo Hristo - 3 months ago 7
Javascript Question

writing JSON object to .json file on server

I'm trying to write my JSON object to a .json file on the server. The way I'm doing this now is:

JavaScript:

function createJsonFile() {

var jsonObject = {
"metros" : [],
"routes" : []
};

// write cities to JSON Object
for ( var index = 0; index < graph.getVerticies().length; index++) {
jsonObject.metros[index] = JSON.stringify(graph.getVertex(index).getData());
}

// write routes to JSON Object
for ( var index = 0; index < graph.getEdges().length; index++) {
jsonObject.routes[index] = JSON.stringify(graph.getEdge(index));
}

// some jQuery to write to file
$.ajax({
type : "POST",
url : "json.php",
dataType : 'json',
data : {
json : jsonObject
}
});
};


PHP:

<?php
$json = $_POST['json'];
$info = json_encode($json);

$file = fopen('new_map_data.json','w+');
fwrite($file, $info);
fclose($file);
?>


It is writing fine and the information seems to be correct, but it is not rendering properly. It is coming out as:

{"metros":["{\\\"code\\\":\\\"SCL\\\",\\\"name\\\":\\\"Santiago\\\",\\\"country\\\":\\\"CL\\\",\\\"continent\\\":\\\"South America\\\",\\\"timezone\\\":-4,\\\"coordinates\\\":{\\\"S\\\":33,\\\"W\\\":71},\\\"population\\\":6000000,\\\"region\\\":1}",


... but I'm expecting this:

"metros" : [
{
"code" : "SCL" ,
"name" : "Santiago" ,
"country" : "CL" ,
"continent" : "South America" ,
"timezone" : -4 ,
"coordinates" : {"S" : 33, "W" : 71} ,
"population" : 6000000 ,
"region" : 1
} ,


Any idea why I'm getting all of these slashes and why it is all on one line?

Thanks,
Hristo

Answer

You are double-encoding. There is no need to encode in JS and PHP, just do it on one side, and just do it once.

// step 1: build data structure
var data = {
    metros: graph.getVerticies(),
    routes: graph.getEdges()
}

// step 2: convert data structure to JSON
$.ajax({
    type : "POST",
    url : "json.php",
    data : {
        json : JSON.stringify(data)
    }
});

Note that the dataType parameter denotes the expected response type, not the the type you send the data as. Post requests will be sent as application/x-www-form-urlencoded by default.

I don't think you need that parameter at all. You could trim that down to:

$.post("json.php", {json : JSON.stringify(data)});

Then (in PHP) do:

<?php
   $json = $_POST['json'];

   /* sanity check */
   if (json_decode($json) != null)
   {
     $file = fopen('new_map_data.json','w+');
     fwrite($file, $json);
     fclose($file);
   }
   else
   {
     // user has posted invalid JSON, handle the error 
   }
?>