Understanding built-in objects: a preliminary study of common built-in objects and their application scenarios

A preliminary study on built-in objects: Understanding common built-in objects and their application scenarios

Introduction:
In JavaScript, built-in objects refer to predefined objects built into JavaScript . These objects can be used directly in code without additional references or imports. Understanding common built-in objects and mastering their usage will greatly improve our efficiency in JavaScript development. This article will introduce some common built-in objects and provide specific code examples to help readers better understand the application scenarios of these objects.

1. String object:
String object is used to process string-related operations. Some of its common methods include:

1. length: Get the length of the string;
2. charAt(index): Return the character at the specified position in the string;
3. indexOf(searchValue, startIndex): Returns the position of the specified string in the original string;
4. slice(startIndex, endIndex): Extracts part of the string;
5. split(separator): Splits the characters Split the string into an array of strings.

Code example:

let str = "Hello, World!";
console.log(str.length);  // 13
console.log(str.charAt(0));  // H
console.log(str.indexOf("World"));  // 7
console.log(str.slice(0, 5));  // Hello
console.log(str.split(","));  // ['Hello', ' World!']

2. Array object:
The Array object is used to process array-related operations. Some of its common methods include:

1. length: Get the length of the array;
2. push(element): Add elements to the end of the array;
3. pop() : Delete and return the last element of the array;
4. join(separator): Combine the array into a string;
5. forEach(callback): Traverse the array and execute the callback function for each element.

Code example:

let arr = [1, 2, 3, 4, 5];
console.log(arr.length);  // 5
arr.push(6);
console.log(arr);  // [1, 2, 3, 4, 5, 6]
console.log(arr.pop());  // 6
console.log(arr.join("-"));  // 1-2-3-4-5
arr.forEach(function(element) {
    console.log(element);
});

3. Math object:
The Math object is used to perform operations related to mathematical calculations. Some of its common methods include:

1. random(): Generate a random number between 0 and 1;
2. ceil(num): Round the number up;
3. floor(num): Round down the logarithm;
4. round(num): Round up the logarithm;
5. max(num1, num2, ...): Returns the maximum value in a set of numbers.

Code examples:

console.log(Math.random());
console.log(Math.ceil(1.2));  // 2
console.log(Math.floor(1.8));  // 1
console.log(Math.round(1.5));  // 2
console.log(Math.max(1, 2, 3, 4, 5));  // 5

Conclusion:
This article introduces common built-in objects in JavaScript and their application scenarios, and provides specific code examples. These built-in objects are often used in JavaScript development, and mastering their usage can help improve development efficiency. Readers can further learn more about the usage of these built-in objects based on actual needs, and flexibly use them in their own projects. Hope this article is helpful to readers!

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