JSFiddle - React, Tailwind, and code Playground

HTML

<p id="demo"></p>

JavaScript

var obj = {
                a: 'a',
                b: 'b',
                c: 'c',
                d: 'd',
                e: 'e',
                f: 'f',
                g: 'g',
                h: 'h',
                i: 'i',
                j: 'j',
                k: 'k',
                l: 'l',
                m: 'm',
                n: 'n',
                o: 'o',
                p: 'p',
                q: 'q',
                r: 'r',
                s: 's',
                t: 't',
                u: 'u',
                v: 'v',
                w: 'w',
                x: 'x',
                y: 'y',
                z: {
                    za: 'za',
                    zb: 'zb',
                    zc: 'zc',
                    zd: 'zd',
                    ze: 'ze',
                    zf: 'zf',
                    zg: 'zg',
                    zh: 'zh',
                    zi: 'zi',
                    zj: 'zj'
                }
            };
            var expTimes = 1000000000, start = 0, end = 0, timeA1 = 0, timeB = 0, timeA2 = 0;

            //不存入變數
            alert('不存入變數速度測試開始')
            start = Date.now();
            for (let i=0;i<expTimes;i++){
                obj.z.zj = i;
            }
            end = Date.now();
            timeA1 = (end - start)/1000;
            alert('不存入變數速度測試結束，耗時 ' + timeA1 + '秒');

            //存入變數
            alert('存入變數速度測試開始')
            start = Date.now();
            var temp = obj.z;
            for (let i=0;i<expTimes;i++){
                temp.zj = i;
            }
            end = Date.now();
            timeB = (end - start)/1000;
            alert('存入變數速度測試結束，耗時 ' + timeB + '秒');

            //不存入變數二次測試
            alert('不存入變數速度再次測試開始')
            start = Date.now();
            for (let i=0;i<expTimes;i++){
                obj.z.zj = i;
            }
            end = Date.now();
            timeA2 = (end - start)/1000;
            alert('不存入變數速度再測試結束，耗時 ' + timeA2 + '秒');
           ...