Add calculated value from an array field to the same array

Not sure if it is possible. I want multiply the "value" field with the "lvalue" field an put the result in a new field "calc" in the corresponding array entry.

Given JSON:

{
  "value": 5,
  "location": [{
    "city": "San Fracisco",
    "lvalue": 10
  },
  {
    "city": "Los Angeles",
    "lvalue": 20
  }]
}

Expected Value in one JSON:

{
  "value": 5,
  "location": [{
    "city": "San Fracisco",
    "lvalue": 10,
    "calc": 50
  },
  {
    "city": "Los Angeles",
    "lvalue": 20,
    "calc": 100
  }]
}

>Solution :

You need to ‘save’ the .value in a variable before looping over the locations to update them using |=:

.value as $val | .location[] |= (.calc = $val * .lvalue)

JqPlay Demo