jquery converts string to number type

In web development, we often need to convert strings into numeric types. For example, the data we get from the backend is generally of string type, but we need to perform calculations and comparisons on the frontend. In JavaScript, use the Number() method or the parseInt() method to convert a string into a numeric type. When developing with jQuery, we can use the $.fn.text() method to get the text content of the element, but this method returns a string type. Therefore, this article will introduce how to use jQuery to convert strings into numeric types.

1. Use the Number() method

Number() method to convert a string into a numeric type. It has the following usages:

Number(value)
Number.parseFloat(value)
Number.parseInt(value, radix)

Among them, value is the string to be converted, parseFloat() and parseInt() are Methods on Number objects.

If value is a non-numeric string, the Number() method will return NaN. If value is a numeric string, the Number() method will return the number. For example:

var str = "123";
var num = Number(str); // 将字符串"123"转换成数字123
console.log(num); // 输出123

var str2 = "abc";
var num2 = Number(str2); // 将字符串"abc"转换成NaN
console.log(num2); // 输出NaN

For the text content obtained using jQuery, we can first use the .text() method to obtain the string, and then convert it into a numeric type. For example:

<div id="price">25.99</div>

var priceStr = $("#price").text(); // 获取元素的文本内容
var priceNum = Number(priceStr); // 将字符串转换成数字
console.log(priceNum); // 输出25.99

2. Use parseInt()method

parseInt()method to convert a string into an integer type . Its syntax is:

parseInt(value, radix)

Among them, value is the string to be converted, and radix represents the base number to be converted. If radix is not specified, the default is decimal.

parseInt()The method parses numbers starting from the left side of the string until a non-numeric character is parsed. If the first character of the string is not a numeric character, the parseInt() method returns NaN. For example:

var num1 = parseInt("123"); // 将字符串"123"转换成数字123
console.log(num1); // 输出123

var num2 = parseInt("123.45"); // 将字符串"123.45"转换成整数123
console.log(num2); // 输出123

var num3 = parseInt("abc"); // 将字符串"abc"转换成NaN
console.log(num3); // 输出NaN

When using the parseInt() method, we need to pay attention to the following points:

• If the string starts with 0x or 0X, it will be Parsed into a hexadecimal number.
• If the string starts with 0, it will be parsed into an octal number. But in use strict mode, this method is disabled.
• Without specifying a base number, if the value starts with 0x or 0X, the radix is ​​16; if it starts with 0, the radix is ​​8; in other cases, the radix is ​​10.

For example:

var num4 = parseInt("0xff"); // 将字符串"0xff"转换成数字255(16进制)
console.log(num4); // 输出255

var num5 = parseInt("077"); // 将字符串"077"转换成数字63(8进制)
console.log(num5); // 输出63

var num6 = parseInt("123", 10); // 将字符串"123"转换成数字123
console.log(num6); // 输出123

var num7 = parseInt("0x10", 16); // 将字符串"0x10"转换成数字16(16进制)
console.log(num7); // 输出16

When using jQuery to obtain the text content, we can first use the $.fn.text() method to obtain the string, and then Use the parseInt() method to convert it to a numeric type. For example:

<div id="quantity">5</div>

var quantityStr = $("#quantity").text(); // 获取元素的文本内容
var quantityNum = parseInt(quantityStr); // 将字符串转换成数字
console.log(quantityNum); // 输出5

Summary

This article introduces how to use jQuery to convert a string into a numeric type. We can use the Number() method to convert a string into a number, or we can use the parseInt() method to convert a string into an integer. When using jQuery to obtain text content, we can first use the .text() method to obtain the string, and then use the corresponding method to convert it into a numeric type.

It should be noted that in some special cases, unexpected situations may occur when using the parseInt() method for conversion. We need to judge and handle it according to the specific situation.

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