提交不调用JavaScript函数

Question

Upon clicking submit, the function doesn't seem to get called and the form submits even if the return is false.

    function validateForm() {
        if (document.getElementById("nm").value="")  {
            alert("You must enter a name!"); 
            return false;
        }
        if (document.getElementById("em").value="")  {
            alert("email required"); 
            return false;
        }
    return true;
    }

And the HTML:

    <form onsubmit=" return validateForm();" action="myscript.php" id="primary">
        <label>Name<input type="text" id="nm"></input></label>
        <label>Email<input type="text" id="em"></input></label>
        <input type="submit" id="send" value="submit"></input>
    </form>

Answer 1

You should use the == or === (exact equal to) to compare values, the = operator is used to assign values.

 function validateForm() {
    if (document.getElementById("nm").value == "")  {
        alert("You must enter a name!"); 
        return false; 
    }

    if (document.getElementById("em").value == "")  {
        alert("email required"); 
        return false; 
    }

    return true;
  }

Answer 2

When making a condition on an if statement the "is equal to" comparison symbol is == or === . = is used for assigning variables.

Answer 3

There's already an answer for that here -> onsubmit method doesn't stop submit

Basically you need to use event.preventDefault() to stop the form submission.