将数组键值添加为对象数组中的键/值

Array
(

    [0] => [{"type":"textarea","label":"Text Area","className":"form-control","name":"textarea-1519387047895","subtype":"textarea"},{"type":"text","label":"Text Field","className":"form-control","name":"text-1519387470117","subtype":"text"}]

    [1] => [{"type":"text","label":"Text Field","className":"form-control","name":"text-1519387050946","subtype":"text"}]

)

I want to add value like this

Array
(

    [0] => [{"type":"textarea","label":"Text Area","className":"form-control","name":"textarea-1519387047895","subtype":"textarea","arraykey":"0"},{"type":"text","label":"Text Field","className":"form-control","name":"text-1519387470117","subtype":"text","arraykey":"0"}]

    [1] => [{"type":"text","label":"Text Field","className":"form-control","name":"text-1519387050946","subtype":"text","arraykey":"1"}]

)

var arr=[
    [{"type":"textarea","label":"Text Area","className":"form-control","name":"textarea-1519387047895","subtype":"textarea"},{"type":"text","label":"Text Field","className":"form-control","name":"text-1519387470117","subtype":"text"}], 
    [{"type":"text","label":"Text Field","className":"form-control","name":"text-1519387050946","subtype":"text"}]
]

for(var i=0; i<arr.length; i++) {
    var innerArr = arr[i];
    for(var j=0; j<innerArr.length; j++) {
        // Add the arraykey key/value to the object
        innerArr[j].arraykey = i
    }
}