Detailed explanation of arguments object in Javascript_Basic knowledge

In the previous article we discussed the default parameters in JavaScript. In this article, we will discuss the arguments parameter object of JavaScript.

For the function in the example below, how can we do different processing according to the different parameters passed in?

Copy code The code is as follows:

function addAll () {
// What do we do here?
}

// Should return 6
addAll(1, 2, 3);

// Should return 10
addAll(1, 2, 3, 4);

Fortunately, JavaScript has an arguments object that can handle the above situation. The arguments object is an array-like object. If you want to know more about the arguments object, please click here. We use the arguments object to change the above example:

Copy code The code is as follows:

function addAll () {
var sum = 0;

for (var i = 0; i < arguments.length; i ) {
        sum = arguments[i];
}

return sum;
}

// Returns 6
addAll(1, 2, 3);

// Returns 10
addAll(1, 2, 3, 4);

We said above that the arguments object is an array-like object, let’s test it:

Copy code The code is as follows:

function getName() {
console.log(Array.isArray(arguments));
}

//will output false
getName("benjamin");

The above test results can be seen:
It is not an array object, so what is the difference between it and an array object? Please click here for details.

Executing the following example will throw an error:

Copy code The code is as follows:

function sortArgs () {
// Uncaught TypeError: undefined is not a function
Sorted = arguments.sort()

return sorted;
}
sortArgs();

We can convert an array-like object into an array object as follows:

Copy code The code is as follows:

function sortArgs () {
// Convert arguments object into a real array
var args = [].slice.call(arguments);

// Now this will work!
Sorted = args.sort()

return sorted;
}

//will output [1, 2, 3]
console.log(sortArgs(1,3,2));

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