JSFiddle - React, Tailwind, and code Playground

JavaScript

var data = [{
    cid: "59eb15be",
    parentCid: "",
    level: 1,
    number: "2",
    subject: "Title 2"
}, {
    cid: "d7d851ef",
    parentCid: "",
    lv: 1,
    number: "4",
    subject: "Title4"
}, {
    cid: "bd01cc50",
    parentCid: "ae35e67d",
    lv: 2,
    number: "1.1",
    subject: "Title1.1"
}, {
    cid: "2d8bd8b0",
    parentCid: "",
    lv: 1,
    number: "3",
    subject: "Title3"
}, {
    cid: "7f66a92d",
    parentCid: "ae35e67d",
    lv: 2,
    number: "1.2",
    subject: "Title1.2"
}, {
    cid: "ae35e67d",
    parentCid: "",
    lv: 1,
    number: "1",
    subject: "Title1"
}, {
    cid: "e7c2dbcc",
    parentCid: "ae35e67d",
    lv: 2,
    number: "1.3",
    subject: "Title1.3"
}, {
    cid: "cc784c42",
    parentCid: "ae35e67d",
    lv: 2,
    number: "1.4",
    subject: "Title1.4"
}];

var data_sorted = data.filter(function(value, index){
    return value.parentCid != "";
}).sort(function(value1, value2){
    return parseFloat(value1.number) - parseFloat(value2.number);
});

console.log(data_sorted);