運算子優先等級

運算子優先等級決定了表達式中執行運算的先後順序，優先等級越高的運算子會越先越先被執行。

一個普通的例子：

3 + 4 * 5 // returns 23

The multiplication operator ("*") has higher precedence than the addition operator ("+") and thus will be evaluated first.

結合性

Associativity determines the order in which operators of the same precedence are processed. For example, consider an expression:

a OP b OP c

Left-associativity (left-to-right) means that it is processed as (a OP b) OP c, while right-associativity (right-to-left) means it is interpreted as a OP (b OP c). Assignment operators are right-associative, so you can write:

a = b = 5;

with the expected result that a and b get the value 5. This is because the assignment operator returns the value that it assigned. First, b is set to 5. Then the a is also set to 5, the return value of b = 5, aka right operand of the assignment.

Table

The following table is ordered from highest (20) to lowest (0) precedence.