jquery determines whether a method exists

When using jQuery, we often need to determine whether a certain method exists. This is very useful in development because we can perform different actions depending on the presence or absence of the method.

jQuery provides two tool functions that can be used to determine whether a method exists. These two functions are:

1. jQuery.isFunction()

This function accepts a parameter and returns a Boolean value to determine whether the incoming parameter is a function.

The following is an example:

if(jQuery.isFunction(someFunction)) {
  // someFunction存在，执行相关操作
} else {
  // someFunction不存在，执行其他操作
}

2. typeof operator

The typeof operator can be used to determine the type of a variable. If the variable type is "function ”, it means it is a function.

The following is an example:

if(typeof someFunction === 'function') {
  // someFunction存在，执行相关操作
} else {
  // someFunction不存在，执行其他操作
}

In addition, if we want to determine whether a method exists on the jQuery object, we can use the hasOwnProperty method of the jQuery.fn object to determine.

The following is an example:

if(jQuery.fn.hasOwnProperty('someMethod')) {
  // someMethod存在，执行相关操作
} else {
  // someMethod不存在，执行其他操作
}

The above three methods can be used to determine whether a function exists, but using the isFunction function provided by jQuery is simpler and more consistent with jQuery's syntax. Habit.

Summary:

When using jQuery, it is very useful to determine whether a method exists. You can perform different operations based on the existence of the method. We can use the isFunction function, typeof operator or the hasOwnProperty method of the jQuery.fn object provided by jQuery to determine whether the method exists. Which method to use can be chosen according to actual needs.

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