js 7 Flashcards

Flashcards covering key JavaScript concepts like 'this' keyword, arrow functions, try-catch, setTimeout, setInterval, and scope.

This keyword

Refers to an object that is executing the current piece of code.

try and catch statement

try = to define a block of code to be tested for errors while it is being executed.

catch = to define a block of code to be executed, if an error occurs in the try block.

try {

console.log(a); // Trying to access an undefined variable

} catch (error) {

console.log('a is not defined'); // Handling the error

}

Arrow Functions

A concise way to write functions in JavaScript.

const func = (arg1, arg2, ...) => { function definition }

const sum = (a, b) => { console.log(a + b); }

const hello = () => { console.log("hello world"); }

setTimeout(function, timeout)

Executes a function once after a specified delay.

setTimeout(function() { console.log("This will be logged after 3 seconds");

}, 3000);

setInterval( function, timeout)

Executes a function repeatedly at specified intervals.

const intervalId = setInterval(function() {

console.log("This will be logged every 2 seconds");

}, 2000);

clearInterval( id)

Used to clear a timeout set by setTimeout().

const intervalId = setInterval(function() {

console.log("This will be logged every 2 seconds");

}, 2000);

// Stop the interval after 10 seconds

setTimeout(function() { clearInterval(intervalId);

console.log("Interval stopped");

}, 10000);

this with Arrow Functions

this is inherited from the parent scope

this with Regular Functions

In a regular function, 'this' refers to the calling object.

const obj = {

value: 42,

regularFunction: function() {

console.log("Regular function: ", this.value);

},

arrowFunction: () => {

console.log("Arrow function: ", this.value);

} };

obj.regularFunction(); // Output: Regular function: 42 obj.arrowFunction(); // Output: Arrow function: undefined (or the value from the outer scope)