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I'm trying to dynamically build a javascript array where _tags is a globally defined array and then send it to php via ajax request. Basically I need the uid as a key and x,y as a sub array. in php it would look something like

$arr[$uid] = array('x'=>$x,'y'=>$y);

but im having trouble figuring out an array like this in javascript, heres what i have

function add_tag_queue(uid,x,y){

    var arr = new Array(3);
    arr[0] = uid;
    arr[1] = x;
    arr[2] = y;

    _tags.push(arr);
}
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5 Answers

up vote 3 down vote accepted

This works ok as long as their is only one entry being added to the array, I'm adding multiple values, in other words the function will run a few times and then i want to send that entire array, but this seems to just be adding everything with a comma delimeter.

Im not sure what youre saying exactly here. The second example i previously gave assumes there is a single x,y pair for each uid but places no limits on how many uids are in _tags. Thats why var _tags = {}; is ourside of the function - so its a global variable.

The following modifications would allow you to have multiple x,y pairs for each uid:

function add_tag_queue(uid,x,y){

   /* 
    * detect if _tags[uid] already exists with one or more values 
    * we assume if its not undefined then the value is an array... 
    * this is similar to doing isset($_tags[$uid]) in php
    */
   if(typeof _tags[uid] == 'undefined'){
     /* 
      * use an array literal by enclosing the value in [], 
      * this makes _tags[uid] and array with eah element of 
      * that array being a hash with an x and y value
      */
     _tags[uid] = [{'x':x,'y':y}]; 
   } else {
     // if _tags[uid] is already defined push the new x,y onto it
     _tags[uid].push({'x':x, 'y':y});
   }
}

This should work:

function add_tag_queue(uid,x,y){

    _tags.push([uid, x,y]);
}

if you want the uid as the key then you need to use an object/hash not an array

var _tags = {}; // tags is an object
function add_tag_queue(uid,x,y){

        _tags[uid] = {'x':x,'y':y};
    }
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This works ok as long as their is only one entry being added to the array, I'm adding multiple values, in other words the function will run a few times and then i want to send that entire array, but this seems to just be adding everything with a comma delimeter. – Brian Dec 3 '10 at 5:51
The second method I think is what I want, but do you have any idea how to convert that into an array in php? – Brian Dec 3 '10 at 5:53
json_decode will decode a json string to a php array. php.net/manual/en/function.json-decode.php – prodigitalson Dec 3 '10 at 6:23
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up vote 0 down vote

You could always just build it in php and json_encode it.

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up vote 0 down vote

You're looking to implement an associative array in Javascript. While Javascript does not support associative arrays, Javascript objects can be treated much the same.

Try this instead:

_tags = {}

function add_tag_queue(uid,x,y){
    _tags[uid] = {x:x, y:y};
}

_tags is now an object and you'll be adding a new object at the uid key. Likewise, the x,y pair is stored in an object. The first x is the key and the second is the value. To clarify, you could write it like this:

function add_tag_queue(uid,xValue,yValue){
    _tags[uid] = {x:xValue, y:yValue};
}
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up vote 0 down vote

It looks very similar to the PHP example you gave:

function add_tag_queue(uid,x,y){
    _tags[uid] = {x: x, y: y};
}
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up vote 0 down vote

This is how I create multidimensional arrays in JS. I hope this helps.

var arr= [];
arr[uid] = new Array();
arr[uid]["x"] = xvalue;
arr[uid]["y"] = yvalue;
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