Add a new element to a JSON array using jq

I have a json as mentioned in the first section and i want to add an element("image": "<IMAGE1_NAME>",) in the json as specified in the expected output.

I tired to use jq like this:

'.containerDefinitions += {"operation":"delete"}'

but this seem to not work. can anyone help me the jq command to achieve the result i want.

{
"taskDefinitionArn": "arn:aws",
"containerDefinitions": [
    {
        "name": "dev-service",
        "cpu": 0,
        "portMappings": [
            {
                "containerPort": 8080,
                "hostPort": 8080,
                "protocol": "tcp"
            }
        ],
        "essential": true,
        "environment": [
            {
                "name": "message",
                "value": "Hi, EMC!!"
            }
        ]
        }
    }
]

}

expected output :

{
"taskDefinitionArn": "arn:aws:ecs:us-west-2:619867110810:task-definition/emc-dev-backend:30",
"containerDefinitions": [
    {
        "name": "dev-service",
        "image": "<IMAGE1_NAME>",
        "cpu": 0,
        "portMappings": [
            {
                "containerPort": 8080,
                "hostPort": 8080,
                "protocol": "tcp"
            }
        ],
        "essential": true,
        "environment": [
            {
                "name": "message",
                "value": "Hi, EMC!!"
            }
        ]
        }
    }
]

}

>Solution :

Since it’s an array, we’ll need some sort of loop, use

.containerDefinitions[] += { "image":"IMAGE1_NAME" }

To add { "image":"IMAGE1_NAME" } on each item in the containerDefinitions key

JqPlay Demo