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In JavaScript, curly braces {} are used to enclose multiple statements in a function, defining the block of code to be executed.

Curly Braces: Curly braces {} are used to group multiple statements into a single block. This is necessary for defining the body of a function, loops, conditional statements, and other control structures.

Usage Example:

function greet(name) {

let greeting = "Hello, " + name;

console.log(greeting);

}

In this example, the curly braces enclose the statements that form the body of the greet function.

References:

MDN Web Docs on Functions

ECMAScript Language Specification

The watchPosition method in the Geolocation API is used to get periodic updates about the geographic location of a user.

watchPosition Method: This method calls the provided callback function with the user's current position as the device's location changes.

Usage Example:

navigator.geolocation.watchPosition(function(position) {

console.log("Latitude: " + position.coords.latitude + ", Longitude: " + position.coords.longitude);

});

In this example, the watchPosition method continuously logs the user's latitude and longitude to the console as the position changes.

References:

MDN Web Docs on watchPosition

W3C Geolocation API Specification

The data type of the variable a is determined by the value assigned to it. In JavaScript, if a value is enclosed in double or single quotes, it is treated as a string.

Variable Assignment:

Given the code:

var a = "true";

The value "true" is enclosed in double quotes, making it a string.

Explanation:

Option A: Boolean is incorrect because the value "true" is a string, not a boolean.

Option B: String is correct because the value is enclosed in double quotes.

Option C: Object is incorrect because the value is a primitive string.

Option D: Undefined is incorrect because the variable a is assigned a value.

References:

MDN Web Docs - JavaScript Data Types

W3Schools - JavaScript Data Types

The CSS property vertical-align: baseline aligns the baseline of the element with the baseline of its parent. For inline elements like images, the baseline alignment means that the bottom of the image aligns with the bottom of the text.

CSS vertical-align Property:

Baseline Alignment: Aligns the baseline of the element with the baseline of its parent.

Example:

Hello World

Analysis:

The element with vertical-align: baseline will align its bottom with the bottom of the surrounding text "Hello World".

References:

MDN Web Docs - vertical-align

W3C CSS Inline Layout Module Level 3