如何正确使用 html 中文本框的值 请帮助我

Question

I wanted to use values from textboxes but failed so i tried with constant values and now I am getting a NAN error. I am showing my result in a label btw.

function myFunction() {
  var translength = 2400
  var transSpacing = 150
  var transEndOverhang = 75
  var transStartOverhang = 75

  var longLength = 6000
  var LongSpacing = 150
  var LongStartOverhang = 75
  var LongEndOverhang = 75

  if (transSpacing != 0)
    document.getElementById('longAmount').value = ((transLength - transStartOverhang - transEndOverhang) / transSpacing) + 1;
  document.getElementById('longAmount').innerHTML = document.getElementById('longAmount').value
  if (document.getElementById('longAmount').value > 0 && transStartOverhang + ((document.getElementById('longAmount').value - 1) * transSpacing) + transEndOverhang < transLength)
    document.getElementById('longAmount').value = longAmount + 1;
  document.getElementById('longAmount').innerHTML = document.getElementById('longAmount').value
}

Answer 1

You're mixing innerHTML and value for the same id. If that id is a textbox you should use .value . Also, to convert strings (the text from the textarea) you can use parseInt() or parseFloat() .

// Here you're taking a bunch of variables and sets the textareas value
document.getElementById('longAmount').value = ((transLength - transStartOverhang - transEndOverhang) / transSpacing) + 1;

// Makes no sense (textarea doesn't have a innerHTML)
document.getElementById('longAmount').innerHTML = document.getElementById('longAmount').value;

// document.getElementById('longAmount').value is a string here
if (document.getElementById('longAmount').value > 0 && transStartOverhang + ((document.getElementById('longAmount').value - 1) * transSpacing) + transEndOverhang < transLength)
    document.getElementById('longAmount').value = longAmount + 1; // longAmount is undefined.

// Again, makes no sense.
document.getElementById('longAmount').innerHTML = document.getElementById('longAmount').value;