Bitwise XORing any number x with 0 yields x. Performs the NOT operator on each bit. NOT a yields the inverted value a. The truth table for the NOT operation is:. The bitwise shift operators take two operands: The direction of the shift operation is controlled by the operator used.
Shift operators convert their operands to bit integers in big-endian order and return a result of the same type as the left operand. The right operand should be less than 32, but if not only the low five bits will be used. This operator shifts the first operand the specified number of bits to the left. Excess bits shifted off to the left are discarded.
Zero bits are shifted in from the right. This operator shifts the first operand the specified number of bits to the right. Excess bits shifted off to the right are discarded. Copies of the leftmost bit are shifted in from the left. Since the new leftmost bit has the same value as the previous leftmost bit, the sign bit the leftmost bit does not change. Hence the name "sign-propagating".
Zero bits are shifted in from the left. The sign bit becomes 0, so the result is always non-negative. For non-negative numbers, zero-fill right shift and sign-propagating right shift yield the same result.
However, this is not the case for negative numbers. The bitwise logical operators are often used to create, manipulate, and read sequences of flags , which are like binary variables.
Variables could be used instead of these sequences, but binary flags take much less memory by a factor of These flags are represented by a sequence of bits: When a flag is set , it has a value of 1. When a flag is cleared , it has a value of 0. Suppose a variable flags has the binary value Since bitwise operators are bit, is actually , but the preceding zeroes can be neglected since they contain no meaningful information.
Typically, a "primitive" bitmask for each flag is defined:. New bitmasks can be created by using the bitwise logical operators on these primitive bitmasks.
Individual flag values can be extracted by ANDing them with a bitmask, where each bit with the value of one will "extract" the corresponding flag. The bitmask masks out the non-relevant flags by ANDing with zeroes hence the term "bitmask". For example, the following two are equivalent:. Flags can be set by ORing them with a bitmask, where each bit with the value one will set the corresponding flag, if that flag isn't already set. For example, the bitmask can be used to set flags C and D:.
Flags can be cleared by ANDing them with a bitmask, where each bit with the value zero will clear the corresponding flag, if it isn't already cleared.
This bitmask can be created by NOTing primitive bitmasks. For example, the bitmask can be used to clear flags A and C:. Flags can be toggled by XORing them with a bitmask, where each bit with the value one will toggle the corresponding flag.
A comparison operator compares its operands and returns a logical value based on whether the comparison is true. The operands can be numerical, string, logical, or object values.
The following table describes the comparison operators in terms of this sample code:. An arithmetic operator takes numerical values either literals or variables as their operands and returns a single numerical value. These operators work as they do in most other programming languages when used with floating point numbers in particular, note that division by zero produces Infinity. A bitwise operator treats their operands as a set of 32 bits zeros and ones , rather than as decimal, hexadecimal, or octal numbers.
The bitwise shift operators take two operands: The direction of the shift operation is controlled by the operator used.
Shift operators convert their operands to thirty-two-bit integers and return a result of the same type as the left operand. Logical operators are typically used with Boolean logical values; when they are, they return a Boolean value. The logical operators are described in the following table. Examples of expressions that can be converted to false are those that evaluate to null, 0, NaN, the empty string "" , or undefined.
As logical expressions are evaluated left to right, they are tested for possible "short-circuit" evaluation using the following rules:. The rules of logic guarantee that these evaluations are always correct.
You can use the conditional operator anywhere you would use a standard operator. This statement assigns the value "adult" to the variable status if age is eighteen or more. Otherwise, it assigns the value "minor" to status. The comma operator , simply evaluates both of its operands and returns the value of the last operand.
This operator is primarily used inside a for loop, to allow multiple variables to be updated each time through the loop. The code prints the values of the diagonal elements in the array:. The delete operator deletes an object, an object's property, or an element at a specified index in an array.
The fourth form is legal only within a with statement, to delete a property from an object. You can use the delete operator to delete variables declared implicitly but not those declared with the var statement. If the delete operator succeeds, it sets the property or element to undefined.
The delete operator returns true if the operation is possible; it returns false if the operation is not possible. When you delete an array element, the array length is not affected. For example, if you delete a , a is still a and a is undefined. When the delete operator removes an array element, that element is no longer in the array.
In the following example, trees is removed with delete. However, trees is still addressable and returns undefined. If you want an array element to exist but have an undefined value, use the undefined keyword instead of the delete operator.
In the following example, trees is assigned the value undefined , but the array element still exists:. The typeof operator is used in either of the following ways:. The typeof operator returns a string indicating the type of the unevaluated operand. The parentheses are optional. For the keywords true and null , the typeof operator returns the following results:. For property values, the typeof operator returns the type of value the property contains:.
The void operator is used in either of the following ways:. The void operator specifies an expression to be evaluated without returning a value. The parentheses surrounding the expression are optional, but it is good style to use them.
You can use the void operator to specify an expression as a hypertext link. The expression is evaluated but is not loaded in place of the current document. The following code creates a hypertext link that does nothing when the user clicks it.