test.html

<!DOCTYPE html>

<meta charset="UTF-8">
<head>
    <script>
        MathJax = {
            tex: {
                inlineMath: []
            },
            svg: {
                fontCache: 'local'
            }
        };
    </script>
    <script src="./tex-svg.js"></script>
    <script>
        function convertLatex() {
            let tex = document.getElementById("inpt").value;
            var mathjax_node = MathJax.tex2svg(tex);
            let screen = document.getElementById("display");
            screen.innerHTML = "";
            screen.appendChild(mathjax_node);
        }
    </script>
</head>

<body>
    <p id="display">
    </p>
    <p id="test">
        中文测试
    </p>
    <textarea id="inpt">
        \begin{equation}
        D(x) = \begin{cases}
        1, & \text{如果 } x \in \mathbb{Q}; \\
        0, & \text{如果 } x \in \mathbb{R};
        \end{cases}
        \end{equation}
    </textarea>
</body>