html - How can I use innerhtml in JavaScript?

Question

My problem is that I don't know how to show the innerhtml of my form.

The form is like a survey form and once you clicked the submit button, all the contents I had answered would show like a summary page...

function displayResult() {
    var first = document.getElementById("first").value;

    var middle = document.getElementById("middle").value;

    var last = document.getElementById("last").value;

    alert("oh");
    var maincontent = document.getElementById("content").innerHTML;
    maincontent = "<p>" + first;

}

Answer 1

var maincontent = document.getElementById("content").innerHTML;
maincontent = "<p>" + first;

On the second line you're overwriting the variable, not setting the .innerHTML. This is what you want:

var maincontent = document.getElementById("content");
maincontent.innerHTML = "<p>" + first;

Also, you must make sure the elements with ids of "first" "middle" and "last" actually exist, or this might cause a TypeError.