SOURCE

const submit = document.getElementById("submit");
        const output = document.querySelector("#output ul");
        const input = document.getElementById("input_area");

        class Line {
            constructor(data) {
                this.type = data.type;
            }
            create() {
                const frag = document.createDocumentFragment();
                const dom = document.createElement('li');
                dom.setAttribute('class', `line ${this.type}`);
                dom.innerHTML = this.html;
                output.appendChild(dom);
            }
        }

        class InLine extends Line {
            constructor(data) {
                super(data);
                this.html = [
                    `<span class="line-deco">&gt;</span>`,
                    `<span class="line-text">${data.text}</span>`,
                ].join('');
            }
        }

        class OutLine extends Line {
            constructor(data) {
                super(data);
                this.html = [
                    `<span class="line-deco out"><▪</span>`,
                    `<span class="line-text">${data.text}</span>`,
                ].join('');
            }
        }

        const fun = {
            send(data) {
                this.renderCalc(data);
                let {text, type} = data;
                let result = {};
                try {
                    result = {
                        text: eval(text),
                        type: 'log'
                    };
                } catch ({message}) {
                    result = {
                        text: message,
                        type: 'error'
                    };
                }
                this.renderResult(result);
            },
            renderCalc(data) {
                const line = new InLine(data);
                line.create();
            },
            renderResult(data) {
                const line = new OutLine(data);
                line.create();
            }
        }

        submit.addEventListener("click", () => {
            fun.send({
                text: input.value,
                type: 'input'
            })
        });

<div id="main">
        <div class="box" id="output">
            <ul>
            </ul>
        </div>
        <div class="box" id="input">
            <textarea name="" id="input_area"></textarea>
        </div>
        <div id="submit">Run</div>
    </div>

html,
        body {
            width: 100%;
            height: 100%;
            margin: 0;
            padding: 0;
            overflow: hidden;
        }

        #main {
           width: 100%;
            height: 100%;
}

        #main .box {
            border: 1px solid #e1e1e1;
            box-sizing: border-box;
            font-size: 15px;
        }

        #output {
            height: 80vh;
        }

        #output ul {
            padding: 10px 5px;
            margin: 0;
        }


        #output .line {
            list-style: none;
            border-bottom: 1px dashed #e1e1e1;
            line-height: 30px;
        }

        #output .line .line-deco {
            font-weight: bold;
            color: #0041d2;
            margin: 0 10px 0 0px;
        }

         #output .line .line-deco.out {
            color: #717171;
        }

        #output .line .line-text.log {
            color: darkslategray;
        }

        #output .line .line-text.error {
            color: red;
        }

        #output .line .line-text.info {
            color: blue;
        }

        #input {
            height: calc( 20vh - 40px);
        }

        #input textarea {
            height: 100%;
            width: 100%;
            outline: none;
            border-width: 0;
            font-size: inherit;
        }

        #submit {
            line-height: 40px;
            vertical-align: middle;
            background-color: darkcyan;
            text-align: center;
            font-weight: bold;
            color: #ffffff;
        }

        #submit:hover {
            background-color: #065d5d;
        }