Array.prototype.map() is a built-in JavaScript method that takes a function as an argument, takes each element of the array in order, and applies the function to create a new array from the array given. The function passed as an argument should return a value inside of the array map function so that it's included in the new array.

For example, the below code will map through an array and double each number. The return statement inside the function ensures that the new value that is calculated will be included in the new array:

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const arr = [2, 4, 6, 8];
const double = arr.map(num => {
  return num * 2;
});

console.log(double); // [4, 8, 12, 16]

You can remove dots from a variable in JavaScript using the replace() method. The syntax is as follows:

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let myVar = "some.string.with.dots.";
myVar = myVar.replace(/[.]/g, '');

The first line of code declares a variable myVar and assigns it to a string with dots. The second line uses the replace() method to remove all dots ([.]) with an empty string ('') globally (g). After running the code, the myVar will now hold somestringwithdots.

This error is caused when the value you are trying to convert to lower case is null or undefined. To fix the error, make sure the value you are trying to convert is defined and has a value. Also, since toLowerCase() is a method on the string prototype, make sure the value is a string. For example:

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let str = 'Hello'; 
str.toLowerCase(); // hello

let str2;
str2.toLowerCase(); // Uncaught TypeError: Cannot read property 'toLowerCase' of undefined

You can log the time in milliseconds using the Date.now() method in JavaScript.

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console.log(Date.now());

Using JavaScript, you can capitalize the first letter in a string with the toUpperCase() method.

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const str = "hello world";

// capitalize the first letter
let result = str.charAt(0).toUpperCase() + str.slice(1);

// print the result
console.log(result); // "Hello world"

In JavaScript, you can use the toUpperCase() method to capitalize a sentence. For example:

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const sentence = "this is a sentence";
const capitalSentence = sentence.toUpperCase();

console.log(capitalSentence);  // THIS IS A SENTENCE

In JavaScript, you can capitalize a word by using the toUpperCase() method on it. For example:

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var word = "hello";
var capitalizedWord = word.toUpperCase();
// Prints "HELLO" 
console.log(capitalizedWord);

In Javascript, you can make an input in a prompt statement case insensitive by using the toLowerCase() method. For example:

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let input = prompt("Enter something").toLowerCase();

By adding the .toLowerCase() method to the end of the prompt statement, the input is automatically converted to all lowercase, despite the user typing in uppercase or lowercase characters.

In JavaScript, you can add items to an array with the push() method. Example code:

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let myArray = ["apple", "orange", "banana"];

myArray.push("kiwi");

console.log(myArray); // Output: ["apple", "orange", "banana", "kiwi"]

In JavaScript, you can use the splice method to delete an item from an array.

The splice method takes two arguments: the index of the item to be deleted and the number of items to delete.

For example, to delete the third item from an array called myArray:

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myArray.splice(2, 1);

The map() method of the Array prototype executes a provided callback for each value in an array and returns a new array containing the results. The provided callback must take three arguments - currentValue, index, and array - and can be written in any of the various supported JavaScript coding languages.

Syntax:

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array.map(callback(currentValue, index, array))

For more information, see Mozilla's Developer Network Guide for map().

To declare value with a prompt in JavaScript, you'll need to use the prompt() method. This method takes in a string of text which will be used as the prompt to request input from the user.

Example code:

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let age = prompt("What is your age?");
console.log("You are "+age+" years old.");

Learn more about prompt() here.

When writing a program, you can send arguments to its main method as a list of strings. For example, in Java we could have:

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public static void main(String[] args) {
  //args is an array of Strings
}

For more information, see the official Java docs.

array.pop is a method used to remove the last element from an array in JavaScript. It can be used in real code as follows:

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let myArray = [1, 2, 3, 4, 5];
let removedElement = myArray.pop();  // removedElement is 5
console.log(myArray); // [1, 2, 3, 4]

For more information, see this documentation.

Replacing something in an array can be accomplished in many different programming languages. For example, in JavaScript, the splice() method can be used to remove existing elements from an array and then replace them with new elements.

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const fruits = ["Banana", "Orange", "Apple", "Mango"];

// Removing 1 element at index 0
fruits.splice(0, 1);

// insert 1 element at index 0
fruits.splice(0, 0, "Lemon");

// change the element at index 0
fruits.splice(0, 1, "Kiwi");

console.log(fruits); 
// Output: ["Kiwi", "Orange", "Apple", "Mango"]

For more information on how to use the splice() method see this MDN article.

To set a JavaScript attribute, you need to use the setAttribute() method. The setAttribute() method accepts two parameters, an attribute and its value. The attribute should be provided as a string and its value can be provided as a string, number, boolean, or any other type.

Here's an example for setting an HTML element's className attribute using setAttribute():

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<div id="example"></div>

// Set the className attribute
document.getElementById("example").setAttribute("className", "my-class");

More information on setAttribute() can be found in the MDN Web Docs.

The Math.max() method returns the largest of zero or more numbers. The syntax for using Math.max() is:

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Math.max(value1, value2 [,value3, ...])

You can also use it to find the maximum of an array. To do so, you would use the apply() method:

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Math.max.apply(null, [value1, value2, value3, ...]);

Here is a full example showing how to use Math.max() with an array:

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const numbers = [1, 12, 4, 18, 9];

const maxValue = Math.max.apply(null, numbers);

console.log(maxValue); // output: 18

Reference:

• JavaScript Math.max()

Math.abs is a method in JavaScript that returns the absolute value of a number.

To use it, you simply pass in the number that you want to find the absolute value of.

For example:

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let x = Math.abs(-3);
console.log(x); // 3 

In JavaScript, an object is a collection of properties, and a property is an association between a name (or key) and a value. A property's value can be a function, in which case the property is known as a method. Objects are the building blocks for modern JavaScript applications and are used to store and manage data.
For more information and example, please see MDN's introduction to Objects.

In JavaScript, you can use the .toLowerCase() string method to convert a string to lowercase. For example:

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let message = "SheCodes ROCKS!";
let result = message.toLowerCase(); // result will be "shecodes rocks!"

Removing elements from an array in most programming languages can typically be done with a remove or splice method. For example, in JavaScript, the splice method can be used to remove an element from an array:

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var letters = ["a", "b", "c" , "d"];

letters.splice(2,1);

// letters is now ["a", "b", "d"]

More details about the splice method can be found here.

You can use an array to set the innerHTML of an element to the correct day of the week by first declaring and initializing an array containing the days of the week. For example:

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let days = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];

Then you can use the getDay() method to get the index of the day in the array, like so:

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let index = new Date().getDay();

Finally, you can use the calculated index value to access the appropriate day of the week string from the array, and set it as the value of the element's innerHTML:

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document.getElementById("elementId").innerHTML = days[index];

You can find more information on the getDay() here.

In JavaScript, the Math.round() method can be used to round a number to the nearest integer. For example:

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let num = 1.24;
let roundedNum = Math.round(num);

console.log(roundedNum); // 1

More information on the Math.round() method can be found here.