What are the javascript selection statements?

The selection statements include: 1. if statement, syntax "if (conditional expression) {//code}else{//code}"; 2. switch statement, syntax "switch (expression) {case Value: statement;break;..}"; 3. Ternary operation statement, syntax "conditional expression?Expression1:Expression2;".

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

1. if statement

This place is similar to ordinary language. The format is as follows:

if(测试条件) {
	测试条件真时执行
}else {
	测试条件假时执行
}

The else can be omitted. For example, the following

if(测试条件) {
	测试条件真时执行
}

can be used in a single line. No need for curly braces, for example

if(3>6) 
	alert("A");
else 
	alert("B");

Multi-branch if statement

This is similar to other languages, multi-branch will only be executed once. The format is as follows:

if (测试条件1) {
	测试条件1true执行语句
}else if(测试条件2) {
	测试条件2true执行语句
}else if(测试条件) {
	测试条件3true执行语句
}else {
	测试条件4true执行语句
}

Nesting of if statements

if(测试条件) {
	if(测试条件) {
		测试条件真时执行
}
}

2. Switch statement

is the same as c, and the syntax format is as follows:

switch(变量) {
	case 值1:
		等于值1执行的语句;
		break;
	case 值2:
		等于值2执行的语句;
		break;	
	case 值3:
		等于值3执行的语句;
		break;
	case 值4:
		等于值4执行的语句;
		break;
	default:
		与上面的值都不相等才执行的语句;
		break;					
}

3. Ternary operation

is similar to c, the format is as follows:

条件表达式？表达式1：表达式2；

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