Convert jquery attribute value to number

jQuery is a widely used JavaScript library that helps developers more easily manipulate HTML documents, handle events, create animations and interactivity, and more. When using jQuery, you often need to convert attribute values ​​​​to numbers in the processing code, so this article will introduce some common methods to achieve this operation.

1. Use the parseInt() function

parseInt() is a built-in function in JavaScript that can convert a string into an integer. The attribute value obtained through jQuery is usually a string type, which needs to be converted to a numeric type when calculating. You can convert a string to a numeric type using the parseInt() method. For example, if we need to convert the width attribute value of an element to a number, we can use the following code:

var width = parseInt($("#element").css("width"), 10);

In this example, $("#element").css("width") will return A string, the parseInt() function will parse it into a number, and the second parameter 10 means to use decimal notation. The result will be assigned to the variable width.

However, it should be noted that if the attribute value is not a valid number, parseInt() will return NaN (not a number). In order to avoid this kind of situation, it is recommended to use isNaN() to check the returned result first, for example:

var width = parseInt($("#element").css("width"), 10);
if(isNaN(width)){
  console.log("无效的属性值");
} else {
  console.log(width);
}

2. Use the parseFloat() function

In addition to parseInt(), there is a similar function is parseFloat(), which converts strings to floating point numbers. If the property value is a string containing a decimal, you can use this to parse it into a number. For example:

var height = parseFloat($("#element").css("height"), 10);

In this example, the parseInt() function is replaced by the parseFloat() function, and the rest is the same.

3. Use the Number() function

The Number() function is another way to convert a string into a number. Unlike parseInt() and parseFloat(), it can handle characters. String numbers before and after the decimal point. For example:

var opacity = Number($("#element").css("opacity"));

4. Use the plus sign ( )

In JavaScript, when adding a string and a number, the string will be converted to a numeric type first, and then the addition calculation will be performed. Similarly, you can also use the plus sign ( ) in jQuery to convert attribute values ​​to numeric types. For example:

var zindex = +($("#element").css("z-index"));

In this example, passing the attribute value to a plus sign ( ) will automatically convert it to a numeric type. The result will be assigned to the variable zindex.

Summary

In this article, we introduced some methods to convert jQuery property values ​​to numeric types. Use parseInt() and parseFloat() to convert string numbers, and use the Number() function to handle strings containing decimal points. In addition, attribute values ​​can also be automatically converted to numeric types using the plus sign ( ). According to the actual situation and needs, it is very important to choose the appropriate method to convert attribute values.

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