This time I will bring you the concept and usage instructions of JS anonymous self-executing functions. What are the precautions regarding the concept and usage of JS anonymous self-executing functions. The following is a practical case, let’s take a look.
1. Common scenarios of anonymous functions
The anonymous function in js is a very common function type, and the more common scenarios are:
<input> <script> //匿名函数的第一种情形 var btn=document.querySelector("#btn"); btn.onclick=function(){ // alert("aaaaa"); } //匿名函数的第二种情形 setInterval(function(){ // alert("bbbbb"); }, 1000); //匿名函数的第三种情形 var fun=function(){ alert("ccccc"); } // fun(); //匿名函数的第四种情形 var obj={ name:"dddd", say:function(){ alert(this.name); } } obj.say(); </script>
The above shows the common usage scenarios of anonymous functions. (Note: querySelector is a new method of finding DOM elements in H5)
2. Anonymous self-executing function
As the name suggests, anonymous self-executing function first It is an anonymous function, but this function can be executed automatically by itself without the help of other elements.
<input> <script> //1,匿名函数的第一种实现方式 (function(data){ // alert(data); })("eee"); //2.匿名自执行函数的第二种实现方式 (function(){ // alert("fff"); }()); //3.匿名自执行函数的第三种实现方式 !function(data){ // alert(data); }("hhh"); //4.匿名自执行函数的第四种实现方式 var fun=function(data){ alert(data); }("iii");</script>
From the above code block, we can conclude that there are generally four ways to implement anonymous self-executing functions.
3. The role of anonymous self-executing functions
①. The most common role of anonymous self-executing functions is to implement closures. I will introduce the concept of closure in detail in a later article. Here is a brief explanation of closures. Closure: Closure is a feature of js. We can use closure to realize the connection inside and outside the function, and can make the local variables of the function always exist in the memory.
②. Anonymous self-executing functions can also be used to simulate the creation of block-level scopes in js, that is, If you use anonymous self-executing functions to wrap some code, you can achieve block-level effects. The effect of the domain is to reduce the number of global variables. After the execution of the anonymous self-executing function is completed, the variables will be released from the memory, thus saving memory.
4. Summary of anonymous functions and anonymous self-executing functions
Anonymous functions can be simply understood as functions without names. There are 4 common scenarios in total. .
Anonymous self-executing functions can be simply understood as anonymous functions that can be executed by themselves. There are four ways to implement anonymous self-executing functions.
I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!
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The above is the detailed content of Concept and usage instructions of JS anonymous self-executing function. For more information, please follow other related articles on the PHP Chinese website!

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