Web Developer preguntas y respuestas de entrevista
Pregunta 11. How does CSS specificity work?
Specificity determines which CSS rule takes precedence when multiple conflicting rules target the same element.
Example:
div#myId {
color: blue;
}
#myId {
color: red;
}
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Pregunta 12. What is AJAX, and how does it work?
AJAX (Asynchronous JavaScript and XML) allows web pages to be updated asynchronously by exchanging small amounts of data with the server behind the scenes.
Example:
var xhr = new XMLHttpRequest();
xhr.open('GET', 'https://api.example.com/data', true);
xhr.onreadystatechange = function() {
if (xhr.readyState == 4 && xhr.status == 200) {
console.log(xhr.responseText);
}
};
xhr.send();
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Pregunta 13. What is responsive web design?
Responsive web design ensures that web applications render well on various devices and window or screen sizes.
Example:
@media screen and (max-width: 600px) {
body {
background-color: lightblue;
}
}
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Pregunta 14. Explain the concept of event delegation in JavaScript.
Event delegation involves using a single event listener to manage all related events for a specific type, reducing the number of event listeners.
Example:
document.getElementById('parentElement').addEventListener('click', function(event) {
if (event.target.tagName === 'BUTTON') {
console.log('Button clicked!');
}
});
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Pregunta 15. What is the purpose of the 'this' keyword in JavaScript?
The 'this' keyword refers to the current execution context and allows access to properties and methods of the current object.
Example:
const person = {
name: 'John',
greet: function() {
console.log('Hello, ' + this.name + '!');
}
};
person.greet();
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