I have tried looking on the Mozilla JSON stringify page of their docs as well as here on SO and Google but found no explanation. I have used JSON.stringify
many time but never come across this result.
I have an array of JSON objects:
[
{
"param_2": "Description 1",
"param_0": "Name 1",
"param_1": "VERSION 1"
},
{
"param_2": "Description 2",
"param_0": "Name 2",
"param_1": "VERSION 2"
},
{
"param_2": "Description 3",
"param_0": "Name 3",
"param_1": "VERSION 3"
}
]
It is attached to my $scope
. In order to POST
them as one parameter, I used the JSON.stringify()
method and receive the following:
[
{
"param_2": "Description 1",
"param_0": "Name 1",
"param_1": "VERSION 1",
"$$hashKey": "005"
},
{
"param_2": "Description 2",
"param_0": "Name 2",
"param_1": "VERSION 2",
"$$hashKey": "006"
},
{
"param_2": "Description 3",
"param_0": "Name 3",
"param_1": "VERSION 3",
"$$hashKey": "007"
}
]
I am just curious about what the $$hashkey
property is exactly, as I expected something more similar to the following from the stringify
method (that is, without the $$hashkey
):
[
{
"1":{
"param_2": "Description 1",
"param_0": "Name 1",
"param_1": "VERSION 1"
},
"2":{
"param_2": "Description 2",
"param_0": "Name 2",
"param_1": "VERSION 2"
},
"3":{
"param_2": "Description 3",
"param_0": "Name 3",
"param_1": "VERSION 3"
}
}
]
I am not sure if it is a factor, but I am using the following:
I'm also using Spring security 3.0.7 on the Server side.
It is not causing me any issues, but I would like to know the cause and reason for the $$hashkey
Angular adds this to keep track of your changes, so it knows when it needs to update the DOM.
If you use angular.toJson(obj)
instead of JSON.stringify(obj)
then Angular will strip out these internal-use values for you.
Also, if you change your repeat expression to use the track by {uniqueProperty}
suffix, Angular won't have to add $$hashKey
at all. For example
<ul>
<li ng-repeat="link in navLinks track by link.href">
<a ng-href="link.href">{{link.title}}</a>
</li>
</ul>
Just always remember you need the "link." part of the expression - I always tend to forget that. Just track by href
will surely not work.