I am using Ext.data.Store to call a PHP script which returns a JSON response with some metadata about fields that will be used in a query (unique name, table, field, and user-friendly title). I then loop through each of the Ext.data.Record objects, placing the data I need into an array (this_column), push that array onto the end of another array (columns), and eventually pass this to an Ext.grid.ColumnModel object.

The problem I am having is - no matter which query I am testing against (I have a number of them, varying in size and complexity), the columns array always works as expected up to columns[15]. At columns[16], all indexes from that point and previous are filled with the value of columns[15]. This behavior continues until the loop reaches the end of the Ext.data.Store object, when the entire arrays consists of the same value.

Here's some code:

columns = [];
this_column = [];

var MetaData = Ext.data.Record.create([
	{name: 'id'},
	{name: 'table'},
	{name: 'field'},
	{name: 'title'}
]);
// Query the server for metadata for the query we're about to run
metaDataStore = new Ext.data.Store({
	autoLoad: true,
	reader: new Ext.data.JsonReader({
		totalProperty: 'results',
		root: 'fields',
		id: 'id'
	}, MetaData),
	proxy: new Ext.data.HttpProxy({
		url: 'index.php/' + type + '/' + slug
	}),
	listeners: {
		'load': function () {
			metaDataStore.each(function(r) {
				this_column['id'] = r.data['id'];
				this_column['header'] = r.data['title'];
				this_column['sortable'] = true;
				this_column['dataIndex'] = r.data['table'] + '.' + r.data['field'];
				// This display valid information, through the entire process
				console.info(this_column['id'] + ' : ' + this_column['header'] + ' : ' + this_column['sortable'] + ' : ' + this_column['dataIndex']);
				columns.push(this_column);
			});

			// This goes nuts at columns[15]
			console.info(columns);

			gridColModel = new Ext.grid.ColumnModel({
				columns: columns
			});