Operator

Description

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+

Addition, e.g. if x is 8 then y = x + 2 results in y becoming 10

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-

Subtraction, e.g. if x is 8 then y = x - 2 results in y becoming 6

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*

Multiplication, e.g. if x is 8 then y = x * 2 results in y becoming 16

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/

Division, e.g. if x is 9 then y = x / 2 results in y becoming 4.5

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%

Modulus (i.e. division remainder), e.g. if x is 9 then y = x % 4 results in y becoming 1

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**

Exponentiation, if x is 8 then y = x ** 5 results in y becoming 32768

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Operator

Description

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+

Plus sign, e.g. if x is 8 then then +x represents -8

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-

Minus sign, e.g. if x is 8 then then -x represents -8

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++

Increment, i.e. add one to the variable. There are technically two different increment operators, the prefix one, and the postfix one. For example, if x is 8 then the statement y = ++x results in x being incremented to 9 and then y assigned this value (i.e. is assigned 9). However, the statement y = x++ involves y being assigned the value of x (i.e. 8) and x then being incremented to 9. For code clarity, some commentators suggest using the statements x = x + 1; y = x; instead of y = ++x and y = x; x = x + 1; instead of y = x++.

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--

Decrement, i.e. subtract one from the variable. There are technically two different decrement operators, the prefix one, and the postfix one. For example, if x is 8 then the statement y = --x results in x being decremented to 7 and then y assigned this value (i.e. is assigned 7). However, the statement y = x-- involves y being assigned the value of x (i.e. 8) and x then being decremented to 7. For code clarity, some commentators suggest using the statements x = x - 1; y = x; instead of y = --x and y = x; x = x - 1; instead of y = x--.

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Operator

Description

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=

Set equal to, e.g. if x is 5 then y = x results in x remaining 5 and y being set to 5

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+=

Set equal to after addition, e.g. if x is 5 and y is 8 then y += x results in x remaining 5 and y = y + x, so y becomes 13

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-=

Set equal to after subtraction, e.g. if x is 5 and y is 8 then y -= x results in x remaining 5 and y = y - x, so y becomes 3

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*=

Set equal to after multiplication, e.g. if x is 5 and y is 8 then y *= x results in x remaining 5 and y = y * x, so y becomes 40

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/=

Set equal to after division, e.g. if x is 5 and y is 8 then y /= x results in x remaining 5 and y = y / x, so y becomes 1.6

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%=

Set equal to after modulus (i.e. division remainder) e.g. if x is 5 and y is 8 then y %= x results in x remaining 5 and y = y % x, so y becomes 3

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**=

Set equal to after exponentiation, e.g. if x is 5 and y is 8 then y **= x results in x remaining 5 and y = y ** x, so y becomes 32768

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Operator

Description

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+

Concatenation, e.g. if x is "a" then y = x + "b" results in y becoming "ab"

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Operator

Description

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=

Set equal to, e.g. if x is "ab" then y = x results in x remaining "ab" and y being set to "ab"

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+=

Set equal to after concatenation, e.g. if x is "a" and y is "b" then y += x results in x remaining "a" and y = y + x, so y becomes "ba"

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Operator

Description

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==

Equal to, e.g. if x is 8 then x==8 is true, but x==5 is false

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===

Equal to and of the same type, e.g. if x is 8 then x===8 is true but x==="8" is false (as not of the same type, although x=="8" would be true, as the computation involves a conversion of "8" to 8)

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!=

Not equal to, e.g. if x is 8 then x!=8 is false, but x!=5 is true

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!==

Not equal to or not of the same type, e.g. if x is 8 then x!== "8" is true (as not of the same type), but x!==8 is false

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> 

Greater than, e.g. if x is 8 then x>8 is false, but x>5 is true

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< 

Less than, e.g. if x is 8 then x<8 is false, but x<11 is true

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>=

Greater than or equal to, e.g. if x is 8 then x>=8 is true, but x>11 is false

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<=

Less than or equal to, e.g. if x is 8 then x<=8 is true, but x<5 is false

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Operator

Description

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var3 = (boolval) ? var1 : var2

Sets var3 equal to var1 if boolval is true, otherwise sets var3 equal to var2

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Operator

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&&

Boolean AND operator, e.g. if x is 5 and y is 8 then (x<6 && y>7) is (true && true), i.e. is true

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||

Boolean OR operator, e.g. if x is 5 and y is 8 then (x<6 && y>10) is (true || false), i.e. is true

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!

Boolean NOT operator, e.g. if x is 5 then !(x==5) is !true, i.e. is false

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Operator

Description

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&

Bitwise AND operator, e.g. 6 & 2 in binary notation is 110 & 010 so is 010, i.e. 2 in decimal notation

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|

Bitwise OR operator, e.g. 6 | 2 in binary notation is 110 | 010 so is 110, i.e. 6 in decimal notation

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~

Bitwise NOT operator, e.g. ~ 6  in binary notation is ~ 110 so is 1(29 times)001, which is interpreted as a negative number so is treated as -7 in decimal notation

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^

Bitwise XOR operator

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<< 

Bitwise left shift operator, e.g. 6 << 2 in binary notation is 110 shifted 2 bits to left so is 11000, i.e. 24 in decimal notation

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>> 

Bitwise right shift operator, e.g. 6 >> 2 in binary notation is 110 shifted 2 bits to the right so is 1, i.e. 1 in decimal notation

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Operator

Description

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delete

Deletes a property from an object

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in

Returns true if the specified property is in the specified object, otherwise false.

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instanceof

Returns true if a specified object is an instance of the specified object type, otherwise returns false

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typeof

Returns the type of a variable, object, function or expression

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yield

yield*

void

Evaluates an expression and then returns undefined

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Operator

Description

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…

Allows an iterable such as an array expression to be expanded where zero or more arguments or elements are expected

,

Evaluates each operand from left to right and returns the value of the last operand (e.g. in a for loop). It is not the same as the comma within arrays, objects and function arguments and parameters