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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