1switch(expression) {
2  case x:
3    // code block
4    break;
5  case y:
6    // code block
7    break;
8  default:
9    // code block
10}

1var gradeOut = 70;
2var totalGrade = 80;
3
4if (gradeOut >= 90)
5    gradeOut+= "My letter grade is: A";
6  else if (totalGrade < 90 && totalGrade >= 80)
7    gradeOut+= "My letter grade is: B";
8  else if (totalGrade < 80 && totalGrade >= 70)
9    gradeOut+= "My letter grade is: C";
10  else if (totalGrade < 70 && totalGrade >= 60)
11    gradeOut+= "My letter grade is: D";
12  else if (totalGrade < 60)
13    gradeOut+= "My letter grade is: F";
14
15//here's the same thing using switch(true). Requires var gradeOut (is currently at top of page
16switch(true) {
17case gradeOut<60:
18    gradeOut= "My letter grade is: F";
19    break;
20case gradeOut<70:
21    gradeOut= "My letter grade is: D";
22    break;
23case gradeOut<80:
24    gradeOut="My letter grade is: C";
25    break;
26}
27

1const randomNumber = Math.floor(Math.random() * 100);
2console.log(randomNumber);
3if (randomNumber < 20) {
4    console.log('randomNumber меньше 20');
5} else if (randomNumber > 50) {
6    console.log('randomNumber больше 50');
7} else { 
8    console.log('randomNumber больше 20, и меньше 50')
9}

1 function alert_msg(){
2                var Name = document.getElementById('name').value
3
4                if (Name == ''){
5                    alert("Must input name");}
6
7               else if (isNaN(Name)){
8                alert("Thank you " +  Name  + " for contacting us!");
9                   
10                }
11                
12                else 
13                alert("Name cannot be a number!");
14            }

1        switch (true) {
2          case bid < 100000:
3            currentIncrease = 1000;
4            break;
5          case type != 1 && bid - 1000 < 100000:
6            currentIncrease = 1000;
7            break;
8          case type != 1 && bid - 2000 < 1000000:
9            currentIncrease = 2000;
10            break;
11          case bid < 1000000:
12            currentIncrease = 2000;
13            break;
14          default:
15            currentIncrease = 10000;
16        }