Let's say you have the following in a file named my.json.

{
  "data": {
    "greeting": [
      {
        "foo": "hello"
      },
      {
        "foo": "world"
      }
    ]
  }
}

Here is how you can parse my.json using jq on a Linux system.

~]$ cat my.json | jq
{
  "data": {
    "greeting": [
      {
        "foo": "hello"
      },
      {
        "foo": "world"
      }
    ]
  }
}

To parse the "data" key.

~]$ cat my.json | jq .data
{
  "greeting": [
    {
      "foo": "hello"
    },
    {
      "foo": "world"
    }
  ]
}

To parse the data and then greeting key.

~]$ cat my.json | jq .data.greeting
[
  {
    "foo": "hello"
  },
  {
    "foo": "world"
  }
]

Or like this, since the greeting key contains a list.

~]$ cat my.json | jq ".data.greeting[]"
[
  {
    "foo": "hello"
  },
  {
    "foo": "world"
  }
]

Let's say you have the following JSON.

{
  "employees": [
    {
      "name": "John Doe",
      "department": "IT"
    },
    {
      "name": "Jane Doe",
      "department": "Sales"
    },
    {
      "name": "Jack Doe",
      "department": "HR"
    }
  ]
}

Here is how you can loop through the .employees list.

jq -c '.employees[]' my.json | while read item; do echo $item; done

Or like this.

while read item; do echo $item; done < <(jq -c '.employees[]' my.json)

Which should return something like this.

{"name": "John Doe", "department": "IT"}
{"name": "Jane Doe", "department": "Sales"}
{"name": "Jack Doe", "department": "HR"}

Let's say you have a JSON file with multiple lists.

{
  "fruits": [
    {
      "color": "red",
      "value": "apple"
    },
    {
      "color": "yellow",
      "value": "banana"
    },
    {
      "color": "green",
      "value": "grapes"
    }
  ],
  "veggies": [
    {
      "color": "white",
      "value": "onion"
    },
    {
      "color": "orange",
      "value": "carrot"
    },
    {
      "color": "green",
      "value": "pepper"
    }
  ]
}

Here is how you can loop through the tops lists (fruits and veggies) 

jq '' my.json | while read item; do echo $item; done

Which should return the following.

{
"fruits": [{"color": "red","value": "apple"},{"color": "yellow","value": "banana"},{"color": "green","value": "grapes"}],
"veggies": [{"color": "white","value": "onion"},{"color": "orange","value": "carrot"},{"color": "green","value": "pepper"}]
}