The usage and difference of each of jQuery

jQuery is a well-known JavaScript library that is often used to simplify JavaScript development. Among them, the $.each() method is a very important function, which can traverse the jQuery object and find the corresponding elements or attributes. In this article, we will delve into the usage and differences of the $.each() method.

1. Basic usage of $.each()

In the jQuery library, the $.each() method is a basic traversal method, used to loop through arrays, objects or jQuery object. Its basic syntax is as follows:

$.each( collection, callback(indexInArray, valueOfElement) )

Among them, the collection parameter refers to the array, object or jQuery object that needs to be traversed, and the callback parameter is a callback function used to perform the corresponding operation for each element. Specifically, the callback function mainly contains two parameters:

indexInArray：表示当前元素在数组或对象中的索引值，对于jQuery对象来说，则表示是当前元素的索引值。
valueOfElement：表示当前元素的具体值。

The following is a simple example of $.each() application:

$.each([1,"A" ,3], function(indexInArray, valueOfElement) {
alert( indexInArray ": " valueOfElement );
});

Here, we use the $.each() method to traverse a containing Arrays of integers, strings, and floating point numbers, and prints the results. The parameters "indexInArray" and "valueOfElement" in the callback function represent the index and actual value of each element in the array respectively.

2. $.each() traverses objects

In addition to arrays and jQuery objects, we can also use the $.each() method to traverse a JavaScript object. Specifically, we can use the $.each() method on an object to traverse each of its properties. Here is a simple example:

var obj = {
name: "Tom",
age: 18,
sex: "Male"
};

$.each(obj, function(key, value) {
alert( key ": " value );
});

Here, we use the $.each() method Iterates over a JavaScript object containing name, age, and sex attributes, and prints the results. The parameters "key" and "value" in the callback function represent the name and value of each attribute respectively.

3. The difference between $.each() method and for loop

In JavaScript development, we can usually also use for loop to traverse arrays or objects. So, we can think about it, what is the difference between the $.each() method and the for loop?

First of all, the $.each() method has better code readability and maintainability than the for loop. Secondly, using the $.each() method ensures that the collection we are traversing is a real array or object. When traversing an object, the $.each() method will automatically box it, and it is difficult for a for loop to handle this type of collection of objects.

In addition, the $.each() method also provides some additional benefits. For example, you can use the break statement to stop a loop inside a callback function. You can also use the this keyword to refer to the current element, which is very useful for event response processing and attribute filtering.

However, it should be noted that for occasions with strict performance requirements, the efficiency of the for loop is higher than the $.each() method, because the $.each() method calls a callback function, which will Efficiency has a certain impact.

Summary

This article provides a detailed introduction to the $.each() method in jQuery, focusing on its basic usage and differences, and also provides some tips for achieving best practices. hint. I hope this article can help you better understand and use the $.each() method.

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