javascript convert array to object for send data by ajax

Question

I would like to send a list of data by ajax. So I push all data in a 2d array

But the ajax of jquery not accept the array data, the data must be object or query string

since the Object of javascript is no push function, I must use array to build the list of data. Is there any function in jquery or javascript, let me

var countLine=$("line").length;
var lines=$("line");
var lineArr=new Array();
var linesArr=new Array();
var x1, y1, x2, y2;
for(i=0; i<countLine; i++)
{
    lineArr['x1']=lines[i].getAttributeNS(null, "x1");
    lineArr['y1']=lines[i].getAttributeNS(null, "y1");
    lineArr['x2']=lines[i].getAttributeNS(null, "x2");
    lineArr['y2']=lines[i].getAttributeNS(null, "y2");
    linesArr.push(lineArr);
}
$.ajax({
    type: "POST",
    url: "test.php",
    data: linesArr,

    async: true,
    cache: false,

    success: function(data){
        $("#txt").text(data);
    },
    error: function(XMLHttpRequest, textStatus, errorThrown){
        alert("fail");
    }
});

Domenic · Accepted Answer · 2011-11-04 21:03:58Z

1

Change

data: linesArr

to

data: { linesArr: linesArr }

This will send an object with a single property, "linesArr", which contains the value of your array.

EDIT: you have a bigger problem. You are trying to store non-numeric properties in an array, as shown in this line:

lineArr['x1']=lines[i].getAttributeNS(null, "x1");

You are also reusing the same lineArr "array" each time through the loop. The following code would work much better:

var lines = $("line");
var linesArray = [];

for (var i = 0; i < lines.length; ++i) {
    var line = lines[i];

    linesArray.push({
        x1: line.getAttributeNS(null, "x1"),
        y1: line.getAttributeNS(null, "y1"),
        x2: line.getAttributeNS(null, "x2"),
        y2: line.getAttributeNS(null, "y2")
    });
}

Then you would access your data like $_POST["linesArr"][0]["x1"].

edited Nov 4, 2011 at 21:03

answered Nov 4, 2011 at 20:04

Domenic

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4 Comments

CL So Over a year ago

I am not sure the data is sent correctly, I have tried different way to get the value, but I cannot get the value echo $_POST[0]['x1']; echo $_POST['x1'][0]; echo $_POST["linesArr"]['x1']; echo $_POST["linesArr"]['x1'][0]; echo $_POST["linesArr"][0]['x1']; echo $_POST[0]["linesArr"]['x1'];

CL So Over a year ago

thank you very much, now is success, and I have found that why I cannot access the data before, because the two word of "data: { linesArr: linesArr }" can not be same, so now the linesArr: linesArray is ok. But one thing I still not understand, why it is a big problem for storing non-numeric properties in an array and reusing the same lineArr "array"?

Domenic Over a year ago

You can reuse the same name; that is not a problem. I changed my sample code to linesArray for clarity because I hate abbreviations, but you can feel free to change it back and things won't break.

Domenic Over a year ago

As for why you shouldn't store non-numeric properties in an array... in JavaScript, as in most other languages, arrays are typical computer-science arrays, i.e. collections indexed by nonnegative numbers. PHP has a thing called an "array" that is really a map from any string to any object, which is confusing; in JavaScript such a map is called an object. So trying to put nonnumeric properties on a JavaScript array (or C# array, or Java array, or C++ array, or Pascal array...) just doesn't make sense, and will give nonsensical results and/or errors.

Jonathan M · Accepted Answer · 2011-11-04 20:04:39Z

1

You need to convert the object to a JSON string using JSON.stringify().

http://json.org/

answered Nov 4, 2011 at 20:04

Jonathan M

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4 Comments

frosty Over a year ago

JSON.stringify(linesArr) to be exact, but this answer is good.

CL So Over a year ago

The JSON.stringify() is also accept Object, so I need convert the array to object first.

Jonathan M Over a year ago

stringify() will accept arrays, objects and scalars. No conversion is necessary.

CL So Over a year ago

Please try these code, in the first alert box, it will display [], while in the second box, it will display {"x":3,"y":4}, so I said it is only accept object. 'code'( var arr=new Array(); var obj=new Object(); arr['x']=1; arr['y']=2; obj.x=3; obj.y=4; alert(JSON.stringify(arr)); alert(JSON.stringify(obj));)

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