Usually I'm using jquery like this, please let's discuss if I could do something better:

I'm loading the jsonfile as a global variable (called jsondata) and loop through it with $.each

In this example I want to get all the Ages for the people with the first name Martin 

$.each(jsondata,function(index,value){

if(value["First Name"] == "Martin"){

console.log(value["Age"]);

}

})

Thank you so much in advance