Develop a webpage using Intrinsic Java Functions
Laboratory Objective:
- To understand basic concepts of Forms in JavaScript.
- To use the given intrinsic functions with specified parameters.
Intrinsic JavaScript Functions
- An intrinsic function (or built-in function) is a function (subroutine) available for use in a given programming language whose implementation is handled specially by the compiler.
- “Intrinsic” is the way some authors refer to what other authors call “built-in”.
- Those data types/objects/classes are always there regardless of what environment you’re running in.
- JavaScript provides intrinsic (or “built-in”) objects. They are the Array, Boolean, Date, Error, Function, Global, JSON, Math, Number, Object, RegExp, and String objects.
- As you know JavaScript is an object oriented programming language, it supports the concept of objects in the form of attributes.
- If an object attribute consists of function, then it is a method of that object, or if an object attribute consists of values, then it is a property of that object.
- For example,
var status = document.readyState;
- readyState is a property of the document object which can contain values such as “unintialized”, ”loading”, ”interactive”, ”complete” whereas,
document.write("Hello World");
- write() is a method of the document object that writes the content “Hello World” on the web page.
- JavaScript Built-in objects such as
- Number
- String
- RegExp
- Array
- Math
- Date
- Boolean
- Each of the above objects hold several built-in functions to perform object related functionality.
isNaN()
- isNaN() method determines whether value of a variable is a legal number or not.
- For example
document.write(isNan(0)); // false
document.write(isNan('JavaScript')); // true
eval()
- eval() is used to execute Javascript source code.
- It evaluates or executes the argument passed to it and generates output.
- For example
eval("var number=2;number=number+2;document.write(number)"); //4
Number()
- Number() method takes an object as an argument and converts it to the corresponding number value.
- Return Nan (Not a Number) if the object passed cannot be converted to a number
- For example
var obj1=new String("123");
var obj2=new Boolean("false");
var obj3=new Boolean("true");
var obj4=new Date();
var obj5=new String("9191 9999");
document.write(Number(obj1)); // 123
document.write(Number(obj2)); // 0
document.write(Number(obj3)); // 1
document.write(Number(obj4)); // 1342720050291
document.write(Number(obj5)); // NaN
String()
- String() function converts the object argument passed to it to a string value.
- For example
document.write(new Boolean(0)); // false
document.write(new Boolean(1)); // true
document.write(new Date()); // Tue Jan 05 2021 13:28:00 GMT+0530
parseInt()
- parseInt() function takes string as a parameter and converts it to integer.
- For example
document.write(parseInt("45")); // 45
document.write(parseInt("85 days")); // 85
document.write(parseInt("this is 9")); // NaN
- An optional radix parameter can also be used to specify the number system to be used to parse the string argument.
- For example,
document.write(parseInt(“10”,16)); //16
parseFloat()
- parseFloat() function takes a string as parameter and parses it to a floating point number.
- For example
document.write(parseFloat("15.26")); // 15.26
document.write(parseFloat("15 48 65")); // 15
document.write(parseFloat("this is 29")); // NaN
document.write(pareFloat(" 54 ")); // 54
- An intrinsic function is often used to replace the Submit button and the Reset button with your own graphical images, which are displayed on a form in place of these buttons.
<html>
<head>
<title>Using Intrinsic JavaScript Functions</title>
</head>
<body>
<FORM name="contact" action="#" method="post">
<P>
First Name: <INPUT type="text" name="Fname"/> <BR>
Last Name: <INPUT type="text" name="Lname"/><BR>
Email: <INPUT type="text" name="Email"/><BR>
<img src="submit.jpg"
onclick="javascript:document.forms.contact.submit()"/>
<img src="reset.jpg"
onclick="javascript:document.forms.contact.reset()"/>
</P>
</FORM>
</body>
</html>
Sample Program
Write a JavaScript function to insert a string within a string at a particular position (default is 1).
<html>
<head>
<title>Insert a string within a specific position in another string</title>
</head>
<body>
<script>
function insert(main_string, ins_string, pos) {
if(typeof(pos) == "undefined") {
pos = 0;
}
if(typeof(ins_string) == "undefined") {
ins_string = '';
}
return main_string.slice(0, pos) + ins_string +
main_string.slice(pos);
}
var main_string = "Welcome to JavaScript";
var ins_string = " the world of ";
var pos = 10;
var final_string = insert(main_string, ins_string, pos);
document.write("Main String: <b>" + main_string + "</b><br/>");
document.write("String to insert: <b>" + ins_string + "</b><br/>");
document.write("Position of string: <b>" + pos + "</b><br/>");
document.write("Final string: <b>" + final_string + "</b>");
</script>
</body>
</html>
