What happens when JavaScript operations lose precision?

In daily programming, we often use various programming languages ​​​​to handle various numerical operations, among which JavaScript is undoubtedly the most widely used one. However, when dealing with complex numerical calculations in some extreme cases, we may encounter situations where the operation results lose precision. So why does this happen? How to avoid loss of calculation precision?

1. Causes of loss of operation precision
   In JavaScript, one of the main reasons for loss of operation precision is the inaccuracy of floating point numbers. There is only one number type in JavaScript, the Number type, which uses 64-bit floating point number representation. The maximum value that can be represented is 1.7976931348623157e 308, and the minimum value is 5e-324. However, during the calculation of decimals, the floating point number Binary representation often cannot be represented accurately, resulting in loss of precision. Take a look at the following example:

console.log(0.1 + 0.2); // 0.30000000000000004

Because binary cannot accurately represent 0.1 and 0.2, the result of their addition is inaccurate in JavaScript, and there are extra digits after the decimal point.

2. How to avoid loss of operation precision
   There are many ways to avoid loss of operation precision. Here are some common methods.

2.1 Use integers for calculation
When performing complex operations, we can convert decimals into integers for calculation, and finally convert the results into decimals. For example, the following code can multiply 0.1 and 0.2 by 10 respectively, then add the results, and finally divide the result by 10:

console.log((0.1 * 10 + 0.2 * 10) / 10); // 0.3

2.2 Use the toFixed() function
Number type in JavaScript Provides a toFixed() method, which can convert a number into a decimal with a specified precision (the number of decimal places placed in parentheses is retained). For example, in the following code, the toFixed() function will retain two decimal places and finally obtain a floating point number with a precision of 0.30.

console.log((0.1 + 0.2).toFixed(2)); // 0.30

2.3 Expanding precision
The operation precision in JavaScript can be expanded to avoid precision loss. A common approach is to convert the decimal to an integer and then perform the calculation. Another option is to use the BigNumber library in JavaScript. This library provides high-precision numerical types, which can greatly improve the accuracy of operations. For example, the following code can use the BigNumber library to solve the problem of loss of operation precision:

var BigNumber = require('bignumber.js');
var x = new BigNumber("0.1");
var y = new BigNumber("0.2");
console.log(x.plus(y).toString()); // "0.3"

This article summarizes the reasons for loss of operation precision in JavaScript and common avoidance methods. When dealing with complex numerical calculations, we need to carefully analyze specific problems, adopt appropriate methods to avoid loss of accuracy, and ensure the correctness of the program.

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