To add AM/PM in time with JavaScript you can use toLocaleTimeString() method. This method converts the time value to a time string using a locale and time options.

For example:

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let currentDate = new Date();
let am_pm = currentDate.toLocaleTimeString();
console.log(am_pm); // 12:48:20 PM

More information can be found on MDN Docs and on W3Schools.

This error indicates that there is an attempt to access the trim() method of an undefined variable. The issue here is that the variable is not being assigned a value (or is being assigned the undefined value) BEFORE the trim() method is called.

In Javascript, ensuring that all variables are assigned values before they are used can be achieved via a concept known as hoisting. Hoisting involves declaring all the variables at the start of the function/block scope and then assigning all the values of the variables after the declaration, which prevents TypeErrors like this one from happening.

For example, a fix for the TypeError described would look something like this:

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let str;
str = "  Hello World  ";
str = str.trim();

More information about hoisting in Javascript can be found here.

In most programming languages, both null and undefined mean basically the same thing - lack of a meaningful value. However, there are some subtle differences. In JavaScript, null is an explicitly assigned value that means "no value", whereas undefined is a variable that has not been assigned a value. Knowing the difference between null and undefined values can be important when deciding how to handle them, as certain functions and operators might behave differently for each. For more information, see this article.

You can make an automatic image slider using JavaScript. The basic idea is to have a series of slides with images and corresponding captions, and have those slides transition automatically by setting the transition property of the slides to a specific time interval. A basic example is given below:

HTML

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<div class="slideshow">
  <div class="slide">
    <img src="image1.jpg" alt="Image 1">
    <p> Caption 1 </p>
  </div>
  <div class="slide">
    <img src="image2.jpg" alt="Image 2">
    <p> Caption 2 </p>
  </div>
  <div class="slide">
    <img src="image3.jpg" alt="Image 3">
    <p> Caption 3 </p>
  </div>
</div>

CSS

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.slideshow {
  max-width: 600px;
  margin: auto;
  position: relative;
}
.slide {
  display: none;
}

JavaScript

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// set index and transition delay
let index = 0;
let transitionDelay = 2000;

// get div containing the slides
let slideContainer = document.querySelector(".slideshow");
// get the slides
let slides = slideContainer.querySelectorAll(".slide");

// set transition delay for slides
for (let slide of slides) {
  slide.style.transition = `all ${transitionDelay/1000}s linear`;
}

// show the first slide
showSlide(index);

// show a specific slide
function showSlide(slideNumber) {
  slides.forEach((slide, i) => {
    slide.style.display = i == slideNumber ? "block" : "none";
  });
  // next index
  index++;
  // go back to 0 if at the end of slides
  if (index >= slides.length) {
    index = 0;
  }
}

// transition to next slide every x seconds
setInterval (() => showSlide(index), transitionDelay);

Variables in JavaScript are containers for storing data values. They can contain any data type, such as numbers, strings, arrays and even other objects. Variables are declared using the var keyword, and can be assigned a value with the = operator. For example:

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var x = 5; 

This declaration creates a variable named x that contains the value 5. Variables in JavaScript are also case-sensitive. For more information, check out the JavaScript documentation.

To convert a timestamp to hours in JavaScript, you can use the getHours() method from the Date object and pass the timestamp as an argument. The following example shows how it would look:

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const timestamp = 1558686613;
const date = new Date(timestamp * 1000);
const hours = date.getHours();
console.log(hours); // Output: 9

You can use the following javascript code to change the background of a div class when a dark mode button is clicked on:

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//Put this code in a document.ready
const darkModeButton = document.querySelector("#dark-mode-button");

darkModeButton.addEventListener("click", ()=> {
    //change the background of the div class with class of "darkMode."
    document.querySelector(".darkMode").style.background = "black";
});

This question requires a code solution. Your code should look like this:

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function isWindy(unit) {
    if (unit > 5) {
      return true;
    }else {
      return false;
    }
}

//test both scenarios:
let metric = isWindy(6); // true
let imperial = isWindy(3); // false

For more information, you can find the reference material on isWindy at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/isWindy.

The code is written in JavaScript and makes use of DOM-related functions, such as document.querySelector to access and manipulate elements of the DOM.

The search() function is being triggered when the user submits the form, indicated by the event listener form.addEventListener set to submit. The purpose of the function is to take the value from the input with the id="city-input" and store it. The event.preventDefault() is then used to actually prevent the form from submitting, since we want to manage the input with JavaScript logic first.

When the value is stored, a conditional is used to check whether the input is empty or not. If it is empty, an alert of the value will be triggered. Otherwise, the innerHTML of h5 is changed to the value of the input.

This is how the code works overall.

For more information on how events work in JavaScript, you can refer to this link.

The most popular string methods are:

1. length(): returns the length of a given string
2. charAt(): returns the specific character at a given index
3. indexOf(): returns the index of the first occurrence of the specified character
4. lastIndexOf(): returns the index of the last occurrence of the specified character
5. replace(): replaces all occurrences of a given character with a specified character
6. toUpperCase(): returns the string in uppercase
7. toLowerCase(): returns the string in lower case
8. trim(): removes all leading and trailing white space
9. valueOf(): returns the primitive value of a string
10. split(): splits a string into an array of strings based on a given delimiter.

References:

• VSCode Documentation
• Java Tutorials Point

The easiest way to remove a character from a string in most programming languages is using the replace() function/method.

For example, in JavaScript:

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var str = "Hello World!";
var res = str.replace("H", ""); // Output: "ello World!"

You can apply two functions, two alerts and two event listeners in Javascript using the addEventListener and removeEventListener methods.

For functions:

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function firstFunc() {
  // do something
}

function secondFunc() {
  // do something
}

For alerts:

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alert("First Alert");
alert("Second Alert");

For event listeners:

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//first Event listener 
document.addEventListener("click", firstFunc);

//second Event listener
document.addEventListener("click", secondFunc);

References:

-MDN web docs - addEventListener()

-MDN web docs - removeEventListener()

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function travel() {
    let name = prompt("What is your name?");
    let email = prompt("What is your email?");
    let travel = prompt("Do you enjoy traveling?");

    if (travel === "yes") {
        alert("Thank you " + name + "! I'll be in touch via email 😁");
    }
    else if (travel !== "yes") 
        alert("Thank you " + name + "! We won't bother you with emails at the moment, but if you change your mind, let us know!");
}

An if/else statement is a control flow statement in many programming languages which allows for code to be executed conditionally. For example, in JavaScript:

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if (x > 0) {
  console.log('x is greater than 0')
} else {
  console.log('x is not greater than 0')
}

For more information, please see the Mozilla documentation.

This can be done in various programming languages. Here is an example in JavaScript:

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function celsiusToFahrenheit(celsius) {
  return celsius * (9/5) + 32; 
}
let fahrenheitTemp = celsiusToFahrenheit(30); // 86

References: Celsius to Fahrenheit Conversion in JavaScript

In most programming languages, you can use the built-in slice() function to get part of an array. For example, in JavaScript you can write the following code to get the first 3 elements of an array arr:

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var arrSlice = arr.slice(0, 3);

The first parameter to slice() is the start index of the part of the array you are trying to get (in this case 0), and the second parameter is the end index of the part (in this case 3). For more details, you can refer to the MDN documentation.

You can use forEach() in order to iterate over all the values nested in objects in an array using JavaScript.

Here's an example that shows how to use forEach() to iterate over object values nested in an array:

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let arr = [
    {
        key1: "value1",
        key2: "value2"
    },
    {
        key1: "value3",
        key2: "value4"
    }
];

arr.forEach(obj => {
    console.log(obj.key1);
    console.log(obj.key2);
});

// Output:
// value1
// value2
// value3
// value4

You can change the class of an HTML element using JavaScript Selectors. To change an element's class, use the classList method. The .toggle() method can be used to add or remove a class from an element:

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document.querySelector("#element").classList.toggle("classname");

This statement will add the specified class to the element if it does not already have the class, or remove it if the element already had the class.

You can also use the .add() and .remove() methods to add or remove a single class from an element, respectively:

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document.querySelector("#element").classList.add("classname");
document.querySelector("#element").classList.remove("classname");

For more information, see MDN's documentation on classList.

In JavaScript, arrays are a type of object used to store multiple values. To create an array, use the Array() constructor function or the [] literal syntax.

For Example:

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// Using Array() constructor
var array = new Array("one", "two", "three");

// Using array literal syntax
var array = ["one", "two", "three"];

An if statement is a type of control flow statement that allows you to execute certain code if a certain condition is met. In most programming languages, an if statement has the following basic syntax:

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if (condition) {
    // Statement(s) will execute if the condition is true
}

Here, condition can be any expression that evaluates to a boolean value - true or false.

For more information on if statements, please refer to this tutorial from W3 Schools.

In JavaScript, you can use the if...else statement to execute code if a certain condition is met. Here is an example of using if...else statement to execute code based on different conditions:

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if (condition1) {
  // code block to be executed if condition1 is true
} else if (condition2) {
  // code block to be executed if the condition1 is false and condition2 is true
} else {
  // code block to be executed if condition1 and condition2 are false
}

For more information, see MDN web docs - An Introduction to Conditional Statements in JavaScript.

In JavaScript, the variables are declared using the keyword var and value is assigned using = operator. For example,

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var x = 10; 

Here, x is a variable and 10 is the value stored in the variable. To print out the value stored in x to the console, we can use the console.log() method as shown below:

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console.log(x); 
// output: 10

For more information, read this article on how to store values into a variable in JavaScript.

In JavaScript, an array of strings can be created using the Array constructor. For example, the following code creates an array containing the strings "Pineapple", "Banana", and "Apple":

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var fruits = new Array("Pineapple", "Banana", "Apple");

An if else statement enables you to control the flow of your program based on a given condition. If a given condition is true, then the program will execute a certain set of statements, otherwise, it will execute the block of code inside the else statement.

In most programming languages you can write an if else statement using the following syntax:

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if (condition) {
  // Statements to be executed if the condition is true
} else {
  // Statements to be executed if the condition is false
}

For example, in the C programming language one could write the following code:

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int x = 10;
if (x == 10) {
  printf("x is equal to 10");
} else {
  printf("x is not equal to 10");
}

The output from this code would be x is equal to 10.

You can use the Array.prototype.includes() method to compare elements from an array and add conditions accordingly.

For example, using JavaScript:

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let arr = [1, 2, 3, 4, 5];

if (arr.includes(3)) {
  console.log('3 is included')
}

More information about Array.prototype.includes() is available in MDN Web Docs for Array.prototype.includes().