So what I'm doing is creating a site that displays information about a person when you click a button. The information is displayed in a text box on a part of the page, and you can click the "Info" button next to the person's name to make the content appear in the text box. The issue I was having was that I couldn't get the content to disappear when I clicked the second "Info" button to get the other person's information to show up. I understand that a function had to be created to change the "display" property to "block" from "none." I understand the first two statements of the function, but once it gets to the "if...return" statement, I don't understand what's going on. Any help in explaining this would be great!
Thanks!
function resetBioVisi()
{
var bioElem = document.getElementById("bio");
var bios = bioElem.childNodes;
if (bios.length == 0) return;
for (var index = 0; index < bios.length; index++)
if (bios[index].style !== undefined)
bios[index].style.display="none";
}
function resetBioVisi()
{
//get bio element by id
var bioElem = document.getElementById("bio");
//get all child elements of bios
var bios = bioElem.childNodes;
//if there are no child elements, do nothing (exit function)
if (bios.length == 0) return;
//otherwise, for each element in the list of bios's child elements...
for (var index = 0; index < bios.length; index++)
//if the element has a style
if (bios[index].style !== undefined)
//set that style to none (make it hidden)
bios[index].style.display="none";
}
function resetBioVisi()
is the function declaration. This is the function name and any parameters.
var bioElem = document.getElementById("bio");
Gets the element with the id "bio" from the dom.
var bios = bioElem.childNodes;
Gets all child nodes of bioElem.
if (bios.length == 0) return;
If bioElem has no children, leave the function immediately and do not continue. The for loop would not run in that case.
for (var index = 0; index < bios.length; index++)
This is a loop. You defined an indexing variable (in this case, index
), a stopping condition, and an iterator. This says "perform the following actions for all children of bioElem
.
if (bios[index].style !== undefined)
Check the style of the current child node. If it is not defined, enter the block. If it is defined, do not enter the block. bios[index]
is saying "Give me the child from bios
at index
position. !==
is saying "If left-hand-side does not equal type or value of undefined".
bios[index].style.display="none"
. This is inside the above condition, so we know bios[index].style
is undefined. We set the display
style to 'hidden'
to hide it from the user's view.
I'll rewrite it in a way that might make more sense to you:
function resetBioVisi() {
var bioElem = document.getElementById("bio");
var bios = bioElem.childNodes;
for (var index = 0; index < bios.length; index++) {
if (bios[index].style !== undefined) {
bios[index].style.display="none";
}
}
}
There are people who came earlier, but anyway this might help you understand it even more:
function resetBioVisi() { // Get the bio element var bioElem = document.getElementById("bio"); // Get all the bio element's children var bios = bioElem.childNodes; // If there are no bio children, return since there's nothing to do if (bios.length == 0) return; // Else, loop through them and set their display style to none so they will not be rendered. for (var index = 0; index < bios.length; index++) if (bios[index].style !== undefined) bios[index].style.display="none"; } var button = document.getElementsByTagName('button')[0]; button.addEventListener('click', resetBioVisi);
<div id="bio"> <p>Bio 1</p> <p>Bio 2</p> <p>Bio 3</p> </div> <button>Hide bios</button>
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