JavaScript statements are commands that perform actions. They are executed sequentially, in the order they are written. Here are some key types of statements:
1. Declarations
- Variable Declarations: Using var, let, and const.
var x = 5;
let y = 10;
const z = 15;
2. Expressions
Expressions are combinations of values, variables, and operators that compute a value.
let a = 5;
let b = 10;
let sum = a + b; // Expression
3. Conditional Statements
These control the flow of execution based on conditions.
- if…else
if (x > 5) {
console.log(‘x is greater than 5’);
} else {
console.log(‘x is less than or equal to 5’);
}
- else if
if (x > 10) {
console.log(‘x is greater than 10’);
} else if (x > 5) {
console.log(‘x is greater than 5 but less than or equal to 10’);
} else {
console.log(‘x is less than or equal to 5’);
}
- switch
switch (x) {
case 5:
console.log(‘x is 5’);
break;
case 10:
console.log(‘x is 10’);
break;
default:
console.log(‘x is neither 5 nor 10’);
}
4. Looping Statements
Loops execute a block of code as long as a specified condition is true.
- for loop
for (let i = 0; i < 5; i++) {
console.log(i);
}
- while loop
let i = 0;
while (i < 5) {
console.log(i);
i++;
}
- do…while loop
let i = 0;
do {
console.log(i);
i++;
} while (i < 5);
5. Functions
Functions are blocks of code designed to perform a particular task.
function greet(name) {
return ‘Hello, ‘ + name;
}
console.log(greet(‘Alice’)); // Output: Hello, Alice
6. Exception Handling
To handle errors gracefully, JavaScript provides try…catch statements.
try {
let result = riskyFunction();
console.log(result);
} catch (error) {
console.error(‘An error occurred:’, error);
} finally {
console.log(‘This code runs regardless of whether an error occurred.’);
}