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Converting to a string

The interesting thing about ECMAScript primitive values for Booleans, numbers, and strings is that they

are pseudo-objects, meaning that they actually have properties and methods. For example, to get the

length of a string, you can do the following:

var sColor = “blue”;

alert(sColor.length); //outputs “4”

Even though the value

“blue”

is a primitive string, it still has a

length

property holding the size of

the string. To that end, the three main primitive values, Booleans, numbers, and strings, all have a

toString()

method to convert their value to a string.

You may be asking, “Isn’t it ridiculously redundant to have a

toString()

method for a string?” Yes,

it is. But ECMAScript defines all objects, whether they are pseudo-objects representing primitive values

or full-fledged objects, to have a

toString()

method. Because the string type falls in the category of

pseudo-object, it also must have a

toString()

method.

The Boolean

toString()

method simply outputs the string

“true”

“false”

, depending on the

value of the variable:

var bFound = false;

alert(bFound.toString()); //outputs “false”

The Number

toString()

method is unique in that it has two modes: default and radix mode. In default

mode, the

toString()

method simply outputs the numeric value in an appropriate string (whether that

is integer, floating point, or e-notation), like this:

var iNum1 = 10;

var fNum2 = 10.0;

alert(iNum1.toString()); //outputs “10”

alert(fNum2.toString()); //outputs “10”

In default mode, the Number ’s

toString()

method always returns the decimal representation of the

number, regardless of how you originally specified it. Therefore, numbers specified by octal or hexadeci-

mal literals are output as decimal.

When you use the Number ’s

toString()

method in radix mode, it is possible to output the number

using a different base, such as 2 for binary, 8 for octal, or 16 for hexadecimal. The

radix

is just a fancy

name for the base to convert to, and it is specified as an argument to the

toString()

method:

var iNum = 10;

alert(iNum1.toString(2)); //outputs “1010”

alert(iNum1.toString(8)); //outputs “12”

alert(iNum1.toString(16)); //outputs “A”

In the previous example, the number 10 is output in three different ways: binary, octal, and hexadecimal.

This functionality can be very useful for dealing with numbers in HTML, which use hexadecimal repre-

sentations for each color.

Chapter 2

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