Various methods in javascript

JavaScript is a programming language used to add dynamic effects and interactivity to web pages. It has many useful methods for manipulating elements in web pages, working with strings and values, creating time intervals and animation effects, and more. In this article, we will discuss some important methods in JavaScript, along with their usage and examples.

1. String method

1. .length
   This method can return the length of any string.

Example:
let string = "Hello World";
console.log(string.length); // The output result is: 11

2. .charAt()
   This method returns the character at the specified index.

Example:
let string = "Hello World";
console.log(string.charAt(3)); // The output result is: 'l'

3. .concat()
   This method can concatenate one or more strings and return a new string.

Example:
let string1 = "Hello";
let string2 = "World";
console.log(string1.concat(" ", string2)); / / The output result is: "Hello World"

4. .indexOf()
   This method returns the position of the first match in the string, or -1 if no match is found. .

Example:
let string = "Hello World";
console.log(string.indexOf("o")); // The output result is: 4

5. .replace()
   This method can replace the text in the string.

Example:
let string = "Hello World";
console.log(string.replace("World", "JavaScript")); // The output result is: " Hello JavaScript"

6. .slice()
   This method can return the specified part of the string.

Example:
let string = "Hello World";
console.log(string.slice(1, 5)); // The output result is: "ello"

2. Array method

1. .length
   This method can return the length of the array.

Example:
let array = [1, 2, 3, 4, 5];
console.log(array.length); // The output result is: 5

2. .push()
   This method adds one or more elements to the end of the array and returns the new length value.

Example:
let array = [1, 2, 3, 4, 5];
console.log(array.push(6)); // The output result is: 6

3. .pop()
   This method can delete the element at the end of the array and return the deleted element.

Example:
let array = [1, 2, 3, 4, 5];
console.log(array.pop()); // The output result is: 5

4. .join()
   This method can combine all elements of the array into a string.

Example:
let array = [1, 2, 3, 4, 5];
console.log(array.join(",")); // Output results It is: "1,2,3,4,5"

5. .splice()
   This method can add or remove elements from the array.

Example:
let array = [1, 2, 3, 4, 5];
array.splice(2, 0, "a", "b");
console.log(array); //The output result is: [1, 2, "a", "b", 3, 4, 5]

6. .sort()
   This method sorts an array.

Example:
let array = [3, 1, 4, 2, 5];
console.log(array.sort()); // The output result is: [ 1, 2, 3, 4, 5]

3. Numerical method

1. .valueOf()
   This method can return the original value of the numerical value.

Example:
let num = 123;
console.log(num.valueOf()); // The output result is: 123

2. . toString()
   This method can convert a numerical value into a string type.

Example:
let num = 123;
console.log(num.toString()); // The output result is: "123"

3. .toFixed()
   This method can retain the specified number of decimal places.

Example:
let num = 3.14159;
console.log(num.toFixed(2)); // The output result is: "3.14"

4. .parseInt()
   This method can convert a string into an integer type.

Example:
let string = "123";
console.log(parseInt(string)); // The output result is: 123

5. .parseFloat()
   This method can convert a string into a floating point number type.

Example:
let string = "3.14159";
console.log(parseFloat(string)); // The output result is: 3.14159

4. Event Method

1. .addEventListener()
   This method can add an event listener for the specified element.

Example:
let button = document.querySelector("button");
button.addEventListener("click", function() {
console.log("Hello World");
});

2. .removeEventListener()
   This method can remove the event listener for the specified element.

Example:
let button = document.querySelector("button");
function handleClick() {
console.log("Hello World");
}
button.addEventListener("click", handleClick);
button.removeEventListener("click", handleClick);

The above are some commonly used methods in JavaScript. Of course there are many other methods, but mastering the above methods can help us become more comfortable in web development.

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