HTML and CSS Reference
Gets code in the form of a string and executes it on the fly.
Encodes and decodes special characters in a plain string.
escape / unescape
Encodes and decodes special characters in a URI string.
encodeUri / decodeUri
Returns true if the specified value is Not-A-Number.
Returns true if the specified value is infinity.
Parses a string and tries to extract an integer number out of it.
Parses a string and tries to extract a floating point number out of it.
that doesn't seem to belong to any objects of yours is ultimately available because it's exposed by the
Null vs. undefined
is not bound to a fixed type. Subsequently, the variable is not bound to any type until it is explicitly
assigned a value. At this stage, the type of the variable is said to be undefined .
unassigned variable using the typeof operator, you get the string undefined . If you instead attempt to
evaluate the content of an unassigned variable, you get null . Pay attention to the following code:
var x; // therefore the type of the variable is "undefined"
var y = null;
What happens if you compare x and y ?
sign ( ===) operator. If you use the == operator, both expressions are evaluated and the resulting
values are compared. However, if you use the === operator, then the types of the values are also
compared. In reference to the previous code snippet, if you compare x and y using the == operator
then you get true, meaning that the undefined value of x ultimately evaluates to null , which matches
the value assigned to y .
In contrast, if you compare x and y using the === operator, then you get false : the two variables
hold the same value but are of different types.