jquery method defines formal parameters

jQuery is a popular JavaScript library widely used in web development. Among them, method definition is the core concept of jQuery, which allows developers to easily define, extend and override methods in jQuery. In the method definition, formal parameters are an essential part. This article will delve into the relevant knowledge of jQuery method definition formal parameters.

1. Introduction

In JavaScript, a function can have one or more parameters, which are variables used inside the function. jQuery's method definition is similar to this, but it has some rules and restrictions of its own. In jQuery, the formal parameter of each method is an object, which contains the following properties:

• #options: defines a set of default parameters that will be combined with the passed parameters to Override passed parameters.
• callback: callback function executed after the method is completed.
• Parameters: Any number of parameters passed to the method.

Below, we will introduce these properties in more detail.

2. options attribute

The options attribute defines a set of key-value pairs for default parameters. If certain parameters are not provided when calling the method, the default values ​​in the options attribute will be used instead. For example, the following is a simple method definition that allows developers to set text and styles:

$.fn.myMethod = function(options) {
  var defaults = {
    text: 'Hello World',
    className: 'my-class'
  };
  var settings = $.extend({}, defaults, options);
  return this.each(function() {
    $(this).text(settings.text).addClass(settings.className);
  });
};

In the above example, the options parameter contains the key-value pair of the default value to be overridden. The $.extend method merges the default value and options objects and stores them in the settings variable. The last line of code sets the text of all selected elements to the set text and adds the set class name.

3. callback attribute

The callback attribute is the function to be executed after the method is completed. For example, the following is a very simple method definition that calls a callback function when executed:

$.fn.success = function(callback) {
  return this.each(function() {
    if (callback && typeof callback === 'function') {
      callback.call(this);
    }
  });
};

In the above example, if the callback parameter is present and is a function, the function will be called after the method is executed implement. We also use the call function to ensure that the callback function runs in the correct scope.

4. Parameters

In addition to the options and callback attributes, methods also allow developers to pass any number of parameters. For example, the following method allows developers to pass a text string and set an opacity change:

$.fn.fadingText = function(text, opacity) {
  return this.each(function() {
    $(this).text(text).animate({opacity: opacity}, 1000);
  });
};

In the above example, we set the text and opacity change on the selected element using the text and opacity parameters . You can pass any number of parameters which will be used inside the method.

5. Summary

jQuery method definition formal parameters is a very familiar part to developers. Defining formal parameters may sound simple, but without understanding the usage of options, callbacks, and parameters in jQuery, the process can become very difficult. Mastering the knowledge of these properties will help developers better understand and extend the methods in jQuery to achieve their own needs.

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