Javascript-返回函数中的数组长度

Question

I'm trying to get an array's length and display it on a page, like so:

var someArray = ['item 1', 'item 2', 'item 3'];

var getArrayLength = function() {
    return someArray.length;
}

getArrayLength();

For some reason this isn't working. I tried to replace the element's innerHTML, same issue.

<p id="demo"></p>
document.getElementById("demo").innerHTML = someArray.length;

Even if I set a variable equal to someArray.length and then return the variable it doesn't work. I don't get any errors, just no result. Is there something special about returning the length of an array in a function?

I was able to pull this off using jQuery, I'm just curious as to what I was doing wrong with the vanilla javascript.

Answer 1

You don't even have to declare any functions.

 var someArray = ['item 1', 'item 2', 'item 3']; document.getElementById("demo").innerHTML = someArray.length; 

 <p id="demo"></p> 

Answer 2

actually your code is working but you are not actually trying to display anything. in your case add something actually giving you output.

var someArray = ['item 1', 'item 2', 'item 3'];

var getArrayLength = function() {
    return someArray.length;
}

console.log(getArrayLength());
alert(getArrayLength());

Answer 3

You have to set the innerHTML (or textContent which is better) after the document is loaded. Try this:

window.addEventListener("load", function() {
    document.getElementById("demo").textContent = someArray.length;
});

jQuery code was working because it's internally waiting for the load event (assuming that you've wrapped your code inside $(function() {...}) ).