JavaScript's self-amplification typical operation (error-prone)

JavaScript "self-increment" operators and expressions

The increment operator (+ +) is a unary operator that increments the operand by 1 at a time. The increment operator requires that its operand be a variable, a property in an object, or an element in an array, and that the type of the operand must be numeric.

If the operand type is not a numeric type, the increment operator converts the its first to numeric data and then increments the operation.

The increment operator (the self-increment operator) has two different increments depending on its position relative to the operand.

1. "Pre-increment" operator

Format:

++a

The pre-increment operator first adds 1 to the value of the operand and then participates in the operation of the expression using the new value of the operand.

Example:

var a=10, B;b=++a;

Results: a=11,b=11

2. "Post-increment" operator

Format:

a++

The post-increment operator first participates in the operation of the operand's value, after which the value of the expression is referenced, and then adds 1 to the value of the operand.

Example:

var a=10, B; b=a++;

Results: a=11,b=10

tip: when "+ +" is in front of a (++a), a plus 1 participates in the expression operation, and when "+ +" is behind A (a++), a first participates in the expression operation, and then adds 1.

"+ +" is only meaningful to a, you can think (++a) or (a++) as a whole, but a first plus 1 to participate in the operation, or to participate in the operation and add 1 of the problem.

　　Case One
var a = 1;
var B = ++a + ++a;
Console.log (b); Result is 5

var a = 1;
var c = a++ + a++;
Console.log (c); Result is 3

var a = 1;
var d = a++ + ++a;
Console.log (d); Result is 4

var a = 1;
var e = ++a + a++;
Console.log (e); Result is 4

　　　

　　Case Two
var a = 1;
var B = ++a + ++a; ==> first a=a+1 get a=2, then 2 + ++a, then a=a+1 get a=3, finally 2+3=5, at this time a value of 3
Console.log (b); Result is 5
var c = a++ + a++; The value of a after the ==> operation is 5
Console.log (c); Result is 7
var d = a++ + ++a; The value of a after the ==> operation is 7
Console.log (d); Result is 12
var e = ++a + a++; The value of a after the ==> operation is 9
Console.log (e); Result is 16

JavaScript "decrement" operator and expression

The decrement operator (the self-decrement operator) has two different ways of decreasing its position relative to the operand, that is, the pre -decrement and post -decrement.

The method of operation above, here is not more verbose.

JavaScript's self-amplification typical operation (error-prone)