In this article we will learn few important concepts of JavaScript, it will be helpful in application development in JavaScript.
Few important utilities in JavaScript
In this article we will learn few important concepts of
JavaScript which might helpful in project development. Let’s learn them one by
one.
print() function to pint page
Printing operation in web application is very common. We
have seen that there is print option in web page and we can get printout of
that page.
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
</head>
<body>
<script>
function printPage() {
window.print();
}
</script>
<input type="button" name="Print" value="Print" onclick="printPage()" />
</body>
</html>
Here is sample example.
escape character in JavaScript
We cannot put double quote (“”) in string. In below article we
have place double quote within string and it will show error.
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
</head>
<body>
<script>
document.write("It is an "escape" character");
</script>
</body>
</html>
To solve this problem we have to use escape ‘\’ before escape
character like below.
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
</head>
<body>
<script>
document.write("They call it an \"escape\" character");
</script>
</body>
</html>
Here is sample output of above code.
Open prompt in JavaScript
Opening prompt in JavaScript is common operation. We can
open prompt by calling prompt() function of window object.
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
</head>
<body>
<script>
function showMessage() {
var value = window.prompt('Enter Name');
console.log(value);
}
</script>
<input type="button" name="prompt" value="Show" onclick="showMessage()" />
</body>
</html>
Here is sample example of above output.
Check function before call
It’s good practice to check function before it call. We can
check whether this function is present or not by checking typeof operator.
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
</head>
<body>
<script>
function hello() {
console.log('I am function');
}
if (typeof hello === "function")
hello();
</script>
</body>
</html>
Implement nested function.
We can implement nested function in JavaScript. In this
example we have implemented nested function in JavaScript.
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
</head>
<body>
<script>
function hypotenuse(a, b) {
function square(x) {
return x * x;
}
return Math.sqrt(square(a) + square(b));
}
console.log(hypotenuse(1, 2));
</script>
</body>
</html>
Conclusion:-
In this article we have learned few important concepts of JavaScript. Hope you have understood them and going to implement in your next
JavaScript application.