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JavaScript if else else if

Conditional statements are used to perform different actions based on different conditions

Conditional Statements

Very often when you write code, you want to perform different actions for different decisions.

You can use conditional statements in your code to do this.

In JavaScript we have the following conditional statements:

  • Use if to specify a block of code to be executed, if a specified condition is true
  • Use else to specify a block of code to be executed, if the same condition is false
  • Use else if to specify a new condition to test, if the first condition is false
  • Use switch to specify many alternative blocks of code to be executed

    • The switch statement is described in the next chapter.

    The if Statement

    Use the if statement to specify a block of JavaScript code to be executed if a condition is true.

    Syntax

    if (condition) {
      //  block of code to be executed if the condition is true
    }

    Note that if is in lowercase letters. Uppercase letters (If or IF) will generate a JavaScript error.

    Example

    Make a "Good day" greeting if the hour is less than 18:00:

    if (hour < 18) {
      greeting = "Good day";
    }

    The result of greeting will be:

    The else Statement

    Use the else statement to specify a block of code to be executed if the condition is false.

    if (condition) {
      //  block of code to be executed if the condition is true
    } else {
      //  block of code to be executed if the condition is false
    }

    Example

    If the hour is less than 18, create a "Good day" greeting, otherwise "Good evening":

    if (hour < 18) {
      greeting = "Good day";
    } else {
      greeting = "Good evening";
    }

    The result of greeting will be:

    The else if Statement

    Use the else if statement to specify a new condition if the first condition is false.

    Syntax

    if (condition1) {
      //  block of code to be executed if condition1 is true
    } else if (condition2) {
      //  block of code to be executed if the condition1 is false and condition2 is true
    } else {
      //  block of code to be executed if the condition1 is false and condition2 is false
    }

    Example

    If time is less than 10:00, create a "Good morning" greeting, if not, but time is less than 20:00, create a "Good day" greeting, otherwise a "Good evening":

    if (time < 10) {
      greeting = "Good morning";
    } else if (time < 20) {
      greeting = "Good day";
    } else {
      greeting = "Good evening";
    }

    The result of greeting will be:

    More Examples

    Random link
    This example will write a link to either w3resource or to the World Wildlife Foundation (WWF). By using a random number, there is a 50% chance for each of the links.

    Test Yourself With Exercises

    Exercise:

    Fix the if statement to alert "Hello World" if x is greater than y.

    if x > y 
  alert("Hello World");

    Start the Exercise

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