Can javascript implement function overloading?

Javascript can implement function overloading. There is an arguments object inside the JavaScript function. You can obtain the parameter list through the arguments object. You can determine the number of parameters and use different methods to simulate the function overloading effect.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

Do JavaScript functions support overloading? Is it possible to implement function overloading? Regarding this issue, there are two main points. First, JavaScript functions; second, overloading.

First, let’s talk about overloading. The so-called overloading, simply put, is a situation where functions or methods have the same name but different parameter lists. Such functions or methods with the same name and different parameters are called overloaded functions or methods. Therefore, overloading mainly requires two points: first, the same function name. Second, different function parameters.

After clarifying the definition of overloading, we return to JavaScript. Tracing back to its origins, when we talk about JavaScript now, we can think of ECMAScript, the standard for JavaScript. So, what specifications are made for functions in this standard?

First of all, ECMAScript has no concept of function signature, because its parameters are represented by arrays containing zero or more values. Without function signatures, true overloading is impossible.

Secondly, if two functions with the same name are defined in ECMAScript, the name only belongs to the function defined later, as follows:

function add(num){
    return num+1;
}
function add(num){
    return num+2;
}
var result = add(4);  //结果为6

In the above example, the add() function It is defined twice. However, when we call it, the second function is called directly. This shows that in JavaScript, the function defined later will overwrite the function defined first.

Having said this, can we conclude that JavaScript does not support function overloading?

Let me introduce an arguments object in JavaScript. First, ECMAScript function parameters are a little different from function parameters in other languages. ECMAScript functions do not care about the number and type of parameters passed in. That is, after you define a function to accept only two parameters, you can still pass zero or more parameters when calling. This will not cause an error. The reason lies in the arguments object. In ECMAScript, the parameters of a function are always stored in an array, and this array can be accessed through the arguments object. So, just use the length attribute to determine how many parameters were passed when calling the function.

Speaking of which, we can try to write like this:

function add(num1, num2){
    if(arguments.length == 1){
        alert("你输入的只有一个数字:"+arguments[0]+" 请重新输入");
    }else if(arguments.length == 2){
        alert("你输入数字的和为：" + arguments[0]+arguments[1]);
}
}

Through this example, we can see that by checking the number of parameters passed in the function, the JavaScript function can make different Reaction, which can indirectly achieve the purpose of overloading.

So, JavaScript can imitate function overloading.

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