Conditions

If / Else

The conditional structure allows code to be executed only if a condition is true.
In English, it can be read as: “If … then … else …”

let age = 18;

if (age >= 18) {
  console.log("Adult");
} else {
  console.log("Minor");
}

Here, if the variable age is greater than or equal to 18, it prints “Adult”.
Otherwise, it prints “Minor”.

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Else If

else if allows testing multiple conditions in sequence.
The program stops as soon as one condition is true.

let grade = 15;

if (grade >= 16) {
  console.log("Excellent");
} else if (grade >= 10) {
  console.log("Average");
} else {
  console.log("Fail");
}

If the grade is 15:

• The 1st condition (grade >= 16) is false
• The 2nd condition (grade >= 10) is true → it prints “Average”.
• The last one is not evaluated.

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Switch

switch is an alternative to multiple if/else if statements, more readable when comparing a single variable against multiple possible values.

let day = "Tuesday";

switch (day) {
  case "Monday":
    console.log("Start of the week");
    break;
  case "Friday":
    console.log("Almost the weekend");
    break;
  default:
    console.log("Regular day");
}

Warning

Without break, execution continues into the following cases (fallthrough effect). The default block runs if no case matches.

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Quick comparison

• If / Else: ideal for testing complex conditions (age > 18 && license === true).
• Switch: more readable when testing one variable against several fixed values (day === “Monday”, day === “Tuesday”, etc.).

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Practical example

let role = "admin";

if (role === "admin") {
  console.log("Full access");
} else if (role === "editor") {
  console.log("Limited access: editing allowed");
} else {
  console.log("Restricted access: read only");
}