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toString

The

Array

object overrides the

toString()

and

valueOf()

methods to return a special string. This

string is made by calling the

toString()

method on each item in the array and then combining them

using commas. For example, an array with the items

“red”

“green”

, and

“blue”

return the string

“red,green,blue”

when either of the methods is called.

var aColors = [“red”, “green”, “blue”];

alert(aColors.toString()); //outputs “red,green,blue”

alert(aColors.valueOf()); //outputs “red,green,blue”

Similarly, the

toLocaleString()

method returns a string made up of the items in the array. The one

difference here is that each of the items’

toLocaleString()

methods is called to get the value. In many

cases, this returns the same value as

toString()

, with the strings joined by commas.

var aColors = [“red”, “green”, “blue”];

alert(aColors.toLocaleString()); //outputs “red,green,blue”

Because developers may also want to create such values out of arrays, ECMAScript provides a method

called

join()

, whose sole purpose it is to create concatenated string values. The

join()

method accepts

one argument, which is the string to use between the items. Consider the following example:

var aColors = [“red”, “green”, “blue”];

alert(aColors.join(“,”)); //outputs “red,green,blue”

alert(aColors.join(“-spring-”)); //outputs “red-spring-green-spring-blue”

alert(aColors.join(“][“)); //outputs “red][green][blue”

Here, the

join()

method is used to create three different string representations of the array. The first,

using the comma, is essentially equal to calling the

toString()

valueOf()

method; the second and

third use different strings to create odd (and probably not that useful) separators between the array

items. The point to understand is that any string can be used as a separator.

You may be wondering at this point, if the

Array

has a way to convert itself into a string, does the

String

have a way to convert itself into an array? The answer is yes. The

String

class has a method

called

split()

that does exactly that. The

split()

method takes only one parameter. That parameter,

as you probably guessed, is the string that should be considered the separator between items. So, if you

have a string separated by commas, you can do the following to convert it into an

Array

var sColors = “red,green,blue”;

var aColors = sColors.split(“,”);

If you specify an empty string as the separator, the

split()

method returns an array in which each item

is equal to one character in the string, for example:

var sColors = “green”;

var aColors = sColors.split(“”);

alert(aColors.toString()); //outputs “g,r,e,e,n”

Here, the string

“green”

is transformed into an array of the strings

“g”

“r”

“e”

, and

“n”

. This

functionality can be useful if you need to parse strings character-by-character.

Chapter 3

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