JavaScript的新手：我可以将List传递给此函数，并且仍然可以使用吗？

Question

As the title says, I'm new to JavaScript and not completely sure on certain syntax's.

After looking for a while I found the following function:

function makeUL(array) {
    // Create the list element:
    var list = document.createElement('ul');

    for (var i = 0; i < array.length; i++) {
        // Create the list item:
        var item = document.createElement('li');

        // Set its contents:
        item.appendChild(document.createTextNode(array[i]));

        // Add it to the list:
        list.appendChild(item);
    }

    // Finally, return the constructed list:
    return list;
}

All I need to know is if I pass a List of Strings into the functions parameter, will it still work, or when it says array is that defining what kind of variable it is? If it won't currently work with a List what needs to change?

Answer 1

when it says array is that defining what kind of variable it is?

No. It is defining the name of the variable that the argument will be assigned to in the scope of the function.

JavaScript (at least ES5 which you are using here) doesn't have any type enforcement for function arguments, so you can pass whatever values you like.

The function does expect the value you pass to be an object with a length property and a number of properties with names that are integers (ie it expects the value to be like an array (see also duck typing )).

List is not a standard JavaScript data type. If you have created a List object, then you can pass it so long as it is array-like.

Answer 2

array is just the name of the expected parameter. It can be of any type (Javascript doesn't have types)

So: Yes, your list will still "work" (as long as it supports the functions that are called on it, of course)

Answer 3

You can pass any Array or Array-like object containing string items, no matter how the parameter is named, and your function will work as expected.

Array-like object is an object, that has a length property with value >=0 and properties 0..length-1 . Array-like object offen does not implement Array methods. The Array can be distinguished from Array-like object using a instanceof Array or Array.isArray(a) , while the typeof a returns 'object' in both cases.

Answer 4

It will still work. Truly speaking in javascript there is an array no list as such. Hence even if you call the function with below arguments:

makeUL(["Cpp","Java","Javascript"])

The output would be :

<ul>
  <li>Cpp</li>
  <li>Java</li>
  <li>Javascript</li>
</ul>

Answer 5

I'm assuming you mean Array. but i think your function is just returning a DOM element, so you wont directly see that in browser unless you append it into DOM tree.

var listofstrings = ['item 1','item 2','item 3'];
document.getElementByName('body').appendChild(makeUL(listofstring));