In JavaScript, operator precedence determines the order in which operators are evaluated in an expression. It is important to understand operator precedence because it can affect the outcome of an expression.
JavaScript has a set of predefined rules that determine the precedence of operators. For example, multiplication and division have a higher precedence than addition and subtraction. This means that multiplication and division will be evaluated before addition and subtraction.
Here is a list of JavaScript operators and their corresponding precedence, from highest to lowest:
- Grouping: ()
- Computed Member Access: []
- Member Access: .
- New (with arguments): new
- Function Call: ()
- Increment/Decrement: ++ —
- Logical Not: !
- Bitwise Not: ~
- Unary Plus: +
- Unary Negation: –
- Typeof: typeof
- Void: void
- Delete: delete
- Multiplication: * / %
- Addition: + –
- Bitwise Shift: << >> >>>
- Relational: < <= > >= in instanceof
- Equality: == != === !==
- Bitwise AND: &
- Bitwise XOR: ^
- Bitwise OR: |
- Logical AND: &&
- Logical OR: ||
- Conditional: ? :
- Assignment: = += -= *= /= %= <<= >>= >>>= &= ^= |=
It is important to note that when operators have the same precedence, their evaluation order is determined by the associativity of the operator. For example, the addition and subtraction operators have the same precedence, so their evaluation order is determined by their associativity. The addition and subtraction operators are left-associative, which means they are evaluated from left to right.
It is always a good practice to use parentheses to make sure that the expressions are evaluated in the order you intended. This can help avoid unexpected outcomes and make the code more readable.
In summary, understanding operator precedence is crucial to writing correct and efficient JavaScript code. Knowing which operators have higher precedence can help you write expressions that evaluate in the order you intended.