Examples of three-mesh operations in JavaScript

In JavaScript, in addition to if ... else and switch statements, there is also a unique three-mesh operator? ...:, also can be used for simple selection structure.

Grammar: Conditions? STATEMENTA:STATEMENTB;

The above statement, first judge the condition condition, if the result is true then executes the statement Statementa, otherwise executes the statement STATEMENTB.
It is noteworthy that because the JavaScript script interpreter will semicolon ";" "As a terminator of a statement, both Statementa and STATEMENTB statements must be a single statement, and multiple statements are used to make an error.

A small example of a three-wood operation

var a=30;
A==20?alert ("established"): Alert ("not established"); To judge a condition? To establish a statement that is only executed: After the statement is not established;

Three-wood operation extended Small instance two

var age=25;

Age>=18?
(
Age<=35? Alert ("You are still young, the future belongs to you!") Alert ("After 35 years old, should pay attention to the body!") ")
) :

Alert ("You are underage!") ");

For example:

var now = new Date ();
var greeting = "good" + (Now.gethours () > 17)? "Evening.": "Day.");

In this example, if it is 6pm, a string containing the "good evening." is created. The equivalent code for using the If...else statement is as follows:

var now = new Date ();
var greeting = "good";
if (Now.gethours () > 17)
Greeting + = "evening."
Else
Greeting + = "Day."

Analysis and example of difference between three-mesh operator and if else

First try the If else, the code is as follows:

if (n >= count-1) {
n = 0;
}else{
n + +;
}
Then the code is finished, ready to optimize the code, the paragraph changed to the three-mesh operator of the wording

n = n >= (count-1)? n=0:n++
The results are completely different.
Then we studied the difference between the two, summed up as a sentence: three mesh operation has a return value, if else no return value
The following tests were done:

var n=1;
if (n>1) {
n=0;
}else{
n++;
}
Console.log (n);
Output Result: 2

The three-mesh operation is as follows:

var n=1;
n = n>1?0:n++;
Console.log (n);
The output is: 1
Insert something else: the difference between ++n and n++: Simply put, it's all n from 1. The difference is that n++ is executed after the statement is added to 1, and ++n do the n+1 before executing the following statement
So what about ++n?
If Else statement

var n=1;
if (n>1) {
n=0;
}else{
++n;
}
Console.log (n);
Output Result: 2

The results of the three-mesh operation

var n=1;
n = n>1?0: ++n;
Console.log (n); The output is: 2

can see if else and three mesh operation of the difference between ~ ~ ~

n++ and ++n in this validation, there is no difference, because if else is the result of the calculation, does not return n, no return value

But for the three-mesh operation, the n++ returns the n value of n itself, ++n returns the value of n as the result of n+1