A function to concatenate field values in a store

Below is a function to concatenate the values in a field in a store. This is similar to Store.sum();

Ext.data.Store.override({
    
    concat: function(field, grouped, separator){
        
        if(typeof separator === 'undefined'){
            separator = ', ';
        }
        
        if (grouped && this.isGrouped()) {
            return this.aggregate(this.getConcat, this, true, [field, separator]);
        } else {
            return this.getConcat(this.data.items, field, separator);
        }    
    },
    
    getConcat: function(records, field, separator){
        var result = [];
        var i = 0;
        var len = records.length;
        
        for(; i < len; ++i){
            result.push(records[i].get(field));
        }
        return result.join(separator);
    }
});  
    

For example, if the store has a field 'email', with data 'a@b.ca' and 'b@c.com', then store.concat('email') would return 'a@b.ca, b@c.com'