JavaScript by Example: JavaScript Core Objects. Pt. 2

<html><head><title>Search and Replace</title>

</head>

Search and Replace Methods<br>

1 var straddr = "DanielSavage@dadserver.org";

document.write( "The original string is "+ straddr + "<br>");

document.write( "The new string is "+

2 straddr.replace("Daniel","Jake")+"<br>");

3 var index=straddr.search("dad");

document.write("The search() method found \"dad\" at

position "+ index +"<br>");

4 var mysubstr=straddr.substr(index,3);

document.write("After replacing \"dad\" with \"POP\" <br>");

5 document.write(straddr.replace(mysubstr,"POP")+"<br>");

</script>

</body></html>

An e-mail address is assigned to the string variable straddr.

The replace() method takes two arguments, the search string and the replacement string. If the substring Daniel is found, it is replaced with Jake.
The search() method takes a subtring as its argument and returns the first position where a substring is found in a string. In this example the substring dad is searched for in the string DanielSavage@dadserver.org and is found at position 13.
The substr() method returns the substring found at position 13, 3 in the string, DanielSavage@dadserver.org: dad.
The substring dad is replaced with POP in the string. (See Figure 9.28.)


var number = new Number(numeric value); var number = Number(numeric value); Example: var n = new Number(65.7);

var number = new Number(numeric value);

var number = Number(numeric value);

Example:

var n = new Number(65.7);

The Number object's properties.
Property	What It Describes
MAX_VALUE	The largest representable number, 1.7976931348623157e+308
MIN_VALUE	The smallest representable number, 5e-324
NaN	Not-a-number value
NEGATIVE_INFINITY	Negative infinite value; returned on overflow
POSITIVE_INFINITY	Infinite value; returned on overflow
prototype	Used to customize the Number object by adding new properties and methods

The Number object's properties.

Property

What It Describes

MAX_VALUE

The largest representable number, 1.7976931348623157e+308

MIN_VALUE

The smallest representable number, 5e-324

NaN

Not-a-number value

NEGATIVE_INFINITY

Negative infinite value; returned on overflow

POSITIVE_INFINITY

Infinite value; returned on overflow

prototype

Used to customize the Number object by adding new properties and methods

The Number object's methods.
Method	What It Does
toString()	Converts a number to a string using a specified base (radix)
toLocaleString()	Converts a number to a string using local number conventions
toFixed()5	Converts a number to a string with a specified number of places after the decimal point
toExponential()	Converts a number to a string using exponential notation and a specified number of places after the decimal point
toPrecision()	Converts a number to a string in either exponential or fixed notation containing the specified number of places after the decimal point

The Number object's methods.

Method

What It Does

toString()

Converts a number to a string using a specified base (radix)

toLocaleString()

Converts a number to a string using local number conventions

toFixed()5

Converts a number to a string with a specified number of places after the decimal point

toExponential()

Converts a number to a string using exponential notation and a specified number of places after the decimal point

toPrecision()

Converts a number to a string in either exponential or fixed notation containing the specified number of places after the decimal point


<html> <head><title>Number Contants</title> </head> <body bgcolor=orange><font color="black" size="+1"> <h2> Constants </h2> <script language="JavaScript"> 1 var largest = Number.MAX_VALUE; 2 var smallest = Number.MIN_VALUE; 3 var num1 = 20; // A primitive numeric value 4 var num2 = new Number(13); // Creating a Number object document.write("<b>The largest number is " + largest+ "<br>"); document.write("The smallest number is "+ smallest + "<br>");
5 document.write("The number as a string (base 2): "+ num1.toString(2)); 6 document.write("<br>The number as a string (base 8): "+ num2.toString(8)); 7 document.write("<br>The square root of -25 is: "+ Math.sqrt(-25) + "<br>"); </script> </body> </html>

<html>

<head><title>Number Contants</title>

</head>

<h2>

Constants

</h2>

1 var largest = Number.MAX_VALUE;

2 var smallest = Number.MIN_VALUE;

3 var num1 = 20; // A primitive numeric value

4 var num2 = new Number(13); // Creating a Number object

document.write("<b>The largest number is " + largest+ "<br>");

document.write("The smallest number is "+ smallest + "<br>");

5 document.write("The number as a string (base 2): "+

num1.toString(2));

6 document.write("<br>The number as a string (base 8): "+

num2.toString(8));

7 document.write("<br>The square root of -25 is: "+

Math.sqrt(-25) + "<br>");

</script>

</body>

</html>


The constant MAX_VALUE is a property of the Number() function. This constant cannot be used with an instance of a Number object.
The constant MIN_VALUE is a property of the Number() function. A number is assigned to the variable called num1. A new Number object is created with the Number() constructor and assigned to num2. The number is converted to a string represented in binary, base 2. The number is converted to a string represented in octal, base 8. The square root of a negative number is illegal. JavaScript returns NaN, not a number, when this calculation is attempted. (See Figure 9.29.)

The constant MAX_VALUE is a property of the Number() function. This constant cannot be used with an instance of a Number object.

The constant MIN_VALUE is a property of the Number() function.
A number is assigned to the variable called num1.
A new Number object is created with the Number() constructor and assigned to num2.
The number is converted to a string represented in binary, base 2.
The number is converted to a string represented in octal, base 8.
The square root of a negative number is illegal. JavaScript returns NaN, not a number, when this calculation is attempted. (See Figure 9.29.)