Note

Random Number

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Math</h2>

<p>Math.floor() used with Math.random() * 101 returns a random integer between 0 and 100 
(both included):</p>

<p id="demo"></p>

<script>
function pollDOM () {
var x ="", i;
for (i=1; i<=20; i++) {
  document.getElementById("demo").innerHTML = Math.floor(Math.random() * 101);
setTimeout(pollDOM, 1000);
}
}
pollDOM ()
</script>

</body>
</html>

Random Integer

function getRandomInteger(min, max) {
  min = Math.ceil(min);
  max = Math.floor(max);
  return Math.floor(Math.random() * (max - min)) + min;
}

Random Float

function getRandomFloat(min, max) {
  return Math.random() * (max - min) + min;
}

Clear Interval

<!DOCTYPE html>
<html>
<body>

<p>A script on this page starts this clock:</p>

<p id="demo"></p>

<button onclick="clearInterval(myVar)">Stop time</button>

<script>
var myVar = setInterval(myTimer ,1000);
function myTimer() {
  var d = new Date();
  document.getElementById("demo").innerHTML = d.toLocaleTimeString();
}
</script>

</body>
</html>

Wait

<!DOCTYPE html>
<html>
<body>

<p>Click "Try it". Wait 3 seconds. The page will alert "Hello".</p>
<p>Click "Stop" to prevent the first function to execute.</p>
<p>(You must click "Stop" before the 3 seconds are up.)</p>

<button onclick="myVar = setTimeout(myFunction, 3000)">Try it</button>

<button onclick="clearTimeout(myVar)">Stop it</button>

<script>
function myFunction() {
  alert("Hello");
}
</script>
</body>
</html>

Get Value of each Element in the form.

<!DOCTYPE html>
<html>
<body>

<form id="frm1" action="/action_page.php">
  First name: <input type="text" name="fname" value="Donald"><br>
  Last name: <input type="text" name="lname" value="Duck"><br><br>
  <input type="submit" value="Submit">
</form> 

<p>Click "Try it" to display the value of each element in the form.</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
  var x = document.getElementById("frm1");
  var text = "";
  var i;
  for (i = 0; i < x.length ;i++) {
    text += x.elements[i].value + "<br>";
  }
  document.getElementById("demo").innerHTML = text;
}
</script>

</body>
</html>

Start & Stop Counter

<!DOCTYPE html>
<html>
<body>

<button onClick="myTimer = setInterval(myCounter, 1000)">Start counter!</button>

<p id="demo">Click on the button above and I will count forever.</p>

<button onClick="clearInterval(myTimer)">Stop counter!</button>

<script>
var c = 0;
function myCounter() {
  document.getElementById("demo").innerHTML = ++c;
}
</script> 

</body>
</html>

Set & Clear Interval

<!DOCTYPE html>
<html>
<body>

<p>A script on this page starts this clock:</p>

<p id="demo"></p>

<button onclick="clearInterval(myVar)">Stop time</button>
<button onclick="myVar = setInterval(myTimer,1000)">Start time</button>

<script>
var myVar = setInterval(myTimer, 1000);
function myTimer() {
  var d = new Date();
  document.getElementById("demo").innerHTML = d.toLocaleTimeString();
  
}


</script>

</body>
</html>

Interval

<!DOCTYPE html>
<html>
<style>
#container {
  width: 400px;
  height: 400px;
  position: relative;
  background: yellow;
}
#animate {
  width: 50px;
  height: 50px;
  position: absolute;
  background-color: red;
}
</style>
<body>

<p><button onclick="myMove()">Click Me</button></p> 

<div id ="container">
  <div id ="animate"></div>
</div>

<script>
function myMove() {
  var elem = document.getElementById("animate");   
  var pos = 0;
  var id = setInterval(frame, 5);
  function frame() {
    if (pos == 350) {
      clearInterval(id);
    } else {
      pos++; 
      elem.style.top = pos + "px"; 
      elem.style.left = pos + "px"; 
    }
  }
}
</script>

</body>
</html>

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Last updated 5 years ago

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