javascript

Chapter 5: Reference Types
The length property can also be helpful in adding items to the end of an array, as in this example:
var colors = [“red”, “blue”, “green”]; //creates an array with three strings
colors[colors.length] = “black”; //add a color (position 3)
colors[colors.length] = “brown”; //add another color (position 4)
T he last item in an array is always at position length – 1 , so the next available open slot is at position
length . Each time an item is added after the last one in the array, the length property is automatically
updated to reflect the change. That means colors[colors.length] assigns a value to position 3 in the
second line of this example and to position 4 in the last line. The new length is automatically calculated
when an item is placed into a position that ’ s outside of the current array size, which is done by adding 1
to the position, as in this example:
var colors = [“red”, “blue”, “green”]; //creates an array with three strings
colors[99] = “black”; //add a color (position 99)
alert(colors.length); //100
In this code, the colors array has a value inserted into position 99, resulting in a new length of 100
(99 + 1). Each of the other items, positions 3 through 98, is filled with undefined .
Arrays can contain a maximum of 4,294,967,295 items, which should be plenty
for almost all programming needs. If you try to add more than that number, an
exception occurs. Trying to create an array with an initial size approaching this
maximum may cause a long - running script error.
Conversion Methods
As mentioned previously, all objects have toLocaleString() , toString() , and valueOf() methods.
The toString() and valueOf() methods return the same value when called on an array. The result is a
comma - separated string that contains the string equivalents of each value in the array, which is to say
that each item has its toString() method called to create the final string. Take a look at this example:
var colors = [“red”, “blue”, “green”]; //creates an array with three strings
alert(colors.toString()); //red,blue,green
alert(colors.valueOf()); //red,blue,green
alert(colors);
//red,blue,green
In this code, the toString() and valueOf() methods are first called explicitly to return the string
representation of the array, which combines the strings, separating them by commas. The last line passes
the array directly into alert() . Because alert() expects a string, it calls toString() behind the
scenes to get the same result as when toString() is called directly.
The toLocaleString() method may end up returning the same value as toString() and valueOf() ,
but not always. When toLocaleString() is called on an array, it creates a comma - delimited string of
the array values. The only difference between this and the two other methods is that toLocaleString()
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