Question 44063 in Html Question posted in
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how do I check if my textbox is empty and run a function javascript,html

i need to run the function changePageTitle() if the textbox with the ID "title" is empty and if not then run newPageTitle = "please choose title" document.title = newPageTitle;
here is my code (I am trying to make something that changes the title of the page to what ever I put in the text box)

<html>

<head>
  <title>
    please choose title
  </title>
</head>

<body>
    <input type="text" id="title" size="150" oninput="changePageTitle()">
  <br>
  <button onclick="changePageTitle()">
    *click me if page title doesn't change
  </button>

  <script type="text/javascript">
    function changePageTitle() {
      newPageTitle = document.getElementById('title').value;
      document.title = newPageTitle;
    }
const interval = setInterval(function(){
  //here is where I want to put the check
}, 1000);
  </script>
</body>

</html>
Tags:

2

Answers


  1. 0 
    const interval = setInterval(function(){
  if(document.getElementById("title").value == ''){
     newPageTitle = "please choose title";
     document.title = newPageTitle;
  }
}, 1000);


    document.getElementById("title").value == ''

    Will return true if the input is empty.

    Is that what you’re after?

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  2. 0

    Simply check the variable directly; you already have an event handler which will be fired on input so setInterval is unnecessary.

    function changePageTitle() {
  let newPageTitle = document.getElementById('title').value;
  if (newPageTitle === '') {
    newPageTitle = "please choose title";
  }
  document.title = newPageTitle;
}

    Try it:

    function changePageTitle() {
  let newPageTitle = document.getElementById('title').value;
  if (!newPageTitle) {
    newPageTitle = "please choose title";
  }
  document.title = newPageTitle;
}
    <html>

<head>
  <title>
    please choose title
  </title>
</head>

<body>
  <input type="text" id="title" size="150" oninput="changePageTitle()">
  <br>
  <button onclick="changePageTitle()">
    *click me if page title doesn't change
  </button>
</body>

</html>
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