Analysis of several definition methods of JS functions_javascript skills

The examples in this article describe several ways to define JS functions. Share it with everyone for your reference, the details are as follows:

The definition of JS functions is relatively flexible. It is different from other languages. Each function is maintained and run as an object.

Let’s take a look at some commonly used definitions:

function func1([parameter]){/*function body*/}
var func2=function([parameter]){/*function body*/};
var func3=function func4([parameter]){/*function body*/};
var func5=new Function();

The first method above is the most commonly used method, needless to say.
The second is to assign an anonymous function to a variable, calling method: func2([function]);
The third method is to assign func4 to the variable func3 and call the method: func3([function]); or func4([function]);
The fourth way is to declare func5 as an object.

Look at their differences:

function func(){
  //函数体
}
//等价于
var func=function(){
  //函数体
}

But they are also defining functions, and there are certain differences in usage.

<script>
//这样是正确的
func(1);
function func(a)
{
  alert(a);
}
</script>

<script>
//这样是错误的，会提示func未定义，主要是在调用func之前没有定义
func(1);
var func = function(a)
{
  alert(a);
}
//这样是正确的，在调用func之前有定义
var func = function(a)
{
  alert(a);
}
func(1);
</script>

The third definition can be understood in the same way.

The fourth definition method also requires declaring the object before it can be referenced.

I hope this article will be helpful to everyone in JavaScript programming.