JavaScript Statements & Declarations

Visualizing fundamental building blocks of code.

Variable Declarations (`var`, `let`, `const`)

Statements used to create and name a variable. `let` and `const` have block scope, while `var` has function scope. `const` also prevents re-assignment.

const name = "Alice";
let age = 30;
var status = "active";
age = 31; // OK
name = "Bob"; // ERROR!

Observe the effects of re-assigning variables.

`const` person:

`let` score:

`var` highscore:

Conditional Statements (`if`, `else if`, `else`)

Statements that execute a block of code if a specified condition is true. If the condition is false, another block can be executed.

if (temperature > 25) {
  // 'It's hot!'
} else {
  // 'It's a good day.'
}

Enter a temperature to see the condition met.

Temperature:

Looping Statements (`for`, `while`)

Statements that execute a block of code a specified number of times, or as long as a condition is true.

for (let i = 0; i < 5; i++) {
  console.log(i);
}

Watch the `for` loop iterate through the items.