JSFiddle - React, Tailwind, and code Playground

JavaScript

var obj = {
    "objectiveDetailId": 285,
        "objectiveId": 29,
        "number": 1,
        "text": "x",
        "subTopics": [{
        "subTopicId": 1,
        "number": 1
    }, {
        "subTopicId": 2,
        "number": 32
    }, {
        "subTopicId": 3,
        "number": 22
    }]
}

obj.subTopics.splice(1, 1)

console.log(obj)