如何将to添加到valueBox输出

<div id="valueBox"></div>

<script>
  var valueBox = document.getElementById("valueBox");
  var to = "to";
  var output = "valueBox输出" + to;

  valueBox.innerHTML = output;
</script>

from flask import Flask

app = Flask(__name__)

@app.route("/")
def valueBox():
    to = "to"
    output = "valueBox输出" + to
    return output

if __name__ == "__main__":
    app.run()