CODEWITHSUNDEEP
javascriptarraysjson
Maurizio Pozzobon
Maurizio Pozzobon

Reputation: 3084

In javascript stringify array does not return expected behavior

I'm getting a weird behavior out of javascript, anyone can help me?

When I click on the 'test' link I get an alert with this string: "[]"

I was expecting something like : "[{'temp':25},{'thermState':'Notte'}]"

What am I doing wrong?

<html>
<head>
    <script type="text/javascript" charset="utf-8" src="js/json2.js"></script>
    <script type="text/javascript" charset="utf-8">

    function test(){
        this.radioStates="";
        this.state = [];
        this.state["temp"]=25;
        this.state["thermState"]="Notte";
        alert(JSON.stringify(this.state));
    }

    </script>
</head>
<body>
<a href="#" onclick="test()">test</a>
</body>
</html>

Upvotes: 3

Views: 784

Answers (4)

kapa
kapa

Reputation: 78741

You could get your expected output by saying:

this.state = [];
this.state[0] = { 'temp' : 25 };
this.state[1] = { 'thermState' : "Notte" };

jsFiddle Demo producing your desired output

Let me try to explain the unexpected behaviour.

In Javascript, everything is an object. When you write this.state = []; your this.state variable becomes an Array object which is empty. You can add elements to it by writing this.state[number] = x or this.state.push(x).

Javascript has no associative arrays. When you write this.state["temp"]=25; you are setting a property on your Array object. You are not putting anything to the array itself. Now this.state will have a property that you can access by this.state.temp or this.state['temp'], but it will not appear in the array itself, because it was not added to that.

Upvotes: 1

Slappy
Slappy

Reputation: 4092

this.state = {}; // Declare as object
this.state["temp"]=25;
this.state["thermState"]="Notte";
alert(JSON.stringify(this.state));

or

this.state = [];
this.state[this.state.length]= {temp: 25};
this.state[this.state.length]= { thermState: "Notte"};
alert(JSON.stringify(this.state));

The first works as an associative array / object, the second works as an array of objects.

Upvotes: 2

Aliostad
Aliostad

Reputation: 81700

You need to use push, if you want state to be an array: 

this.state.push({"temp":25, "thermState": "Notte"});

Upvotes: 0

Royi Namir
Royi Namir

Reputation: 148744

change to : 

this.state = {}; ................

properties can be added to object not to arrays.

Upvotes: 6

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