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JavaScript. W3Schools in English. Lessons for beginners

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JavaScript Conditionals

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Conditional Statements

When you write code, you often want to perform different actions for different conditions.

Conditional statements run different code depending on a true or false condition.

Conditional statements include:

  • if
  • if...else
  • if...else if...else
  • switch
  • ternary (? :)

When to use Conditionals

  • Use if to specify a code block to be executed, if a specified condition is true
  • Use else to specify a code block 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 code blocks to be executed
  • Use (? :) (ternary) as a shorthand for if...else

The if Statement

Use if to specify a code block to be executed, if a specified condition is true.

Syntax

if (condition) {
  // code to execute if the condition is true
}

The else Statement

Use else to specify a code block to be executed, if the same condition is false.

Syntax

if (condition) {
  // code to execute if the condition is true
} else {
  // code to execute if the condition is false
}

The else if Statement

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

Syntax

if (condition1) {
  // code to execute if condition1 is true
} else if (condition2) {
  // code to execute if the condition1 is false and condition2 is true
} else {
  // code to execute if the condition1 is false and condition2 is false
}

The switch Statement

Use switch to specify many alternative code blocks to be executed.

Syntax

switch(expression) {
  case x:
    // code block
    break;
  case y:
    // code block
    break;
  default:
    // code block
}

Ternary Operator (? :)

Use (? :) (ternary) as a shorthand for if...else.

Example

condition ? expression1 : expression2
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