javascript sets numerical range

JavaScript is a popular scripting language that has become a necessary skill for the development of websites and applications. Among them, setting the numerical range is a very important part of the development process. This article will explore how to set the numerical range in JavaScript.

JavaScript provides methods to easily define and limit numerical ranges. The following are several commonly used methods:

1. Math.max() and Math.min()

The Math.max() method can be used to compare multiple The size of the number, the largest number will be used as the return value. Similarly, the Math.min() method can be used to compare the sizes of multiple numbers, and the smallest number will be used as the return value.

For example:

Math.max(5,10,20);
// 返回值为20

Math.min(5,10,20);
// 返回值为5

In daily development, we can use these two methods to limit the numerical range. For example, if we want to ensure that a number is not less than 0, we can write:

let num = Math.max(0, inputNum);
// 此处的inputNum为用户输入的数值

2. parseInt()

The parseInt() method can convert a string to integer. If parsing fails, NaN (not a number) will be returned.

When we get a value from the input box, we usually get a string, so we need to use the parseInt() method to convert it to an integer. For example:

let inputNumStr = document.getElementById("input").value;
let inputNum = parseInt(inputNumStr);

It should be noted that if the string cannot be parsed into a number, NaN will be returned. Therefore, an error handling mechanism needs to be added to handle this situation.

if (isNaN(inputNum)) {
  console.error("输入值不合法");
}

3. isNaN()

The isNaN() method is used to check whether a value is NaN. If it is NaN, return true, otherwise return false.

isNaN(NaN); //true
isNaN(123); //false

We can use the isNaN() method in conjunction with the parseInt() method to ensure that the value obtained from the input box is a number.

let inputNumStr = document.getElementById("input").value;
let inputNum = parseInt(inputNumStr);

if (isNaN(inputNum)) {
  console.error("输入值不合法");
}

4. Number.isNaN()

Similar to the isNaN() method, the Number.isNaN() method is used to check whether a value is NaN. The difference is that it returns true only if the argument is NaN.

Number.isNaN(NaN); //true
Number.isNaN(123); //false
Number.isNaN("123"); //false

When using it, we need to pay attention to the scenario of using the Number.isNaN() method. If you want to check whether a value is a number, you still need to use the isNaN() method.

5. Numerical comparison

We can also use comparison operators (<, >, <=, >=) to limit the numerical range.

For example, if we want to ensure that a value num is between 0 and 100, we can write like this:

if (num < 0) {
  num = 0;
} else if (num > 100) {
  num = 100;
}

This method is more intuitive, but it needs to consider a variety of situations and boundary conditions, Relatively error-prone.

To sum up, the above five methods are common ways to set the numerical range in JavaScript. When developing code, we can choose appropriate methods according to actual needs and add corresponding error handling mechanisms to ensure the correctness and reliability of the code.

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