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JavaScript JavaScript and the DOM (Retiring) Traversing the DOM Child Traversal

Matt Davis
Matt Davis
13,372 Points
Posted by Matt Davis
Matt Davis
13,372 Points

can not read property 1 of null

the paragraphs turn blue and I wrote the values to the screen to confirm is this a bug?

app.js 
var section = document.querySelector('section');
var paragraphs;
paragraphs = section.children
var i; 

for(i=0; i <= paragraphs.length; i++)
{paragraphs[i].style.color='blue';
document.write(paragraphs[i].textContent);}
index.html 
<!DOCTYPE html>
<html>
    <head>
        <title>Child Traversal</title>
    </head>
    <body>
        <section>
            <p>This is the first paragraph</p>
            <p>This is a slightly longer, second paragraph</p>
            <p>Shorter, last paragraph</p>
        </section>
        <footer>
            <p>&copy; 2019</p> 
        </footer>
        <script src="app.js"></script>
    </body>
</html>

1 Answer

Jorge Flores
Jorge Flores
2,207 Points

Your loop should use '<' not '<='. Your counter starts at 0 and goes to 3 (and includes it), thats four iterations even though there are 3 paragraphs which results in an error as the last iteration is on a non-existing paragraph. If you use '<' then only 3 iterations are done on 3 existing paragraphs. Hope that helps!

Matt Davis
Matt Davis
13,372 Points
Matt Davis
Matt Davis
13,372 Points

That makes perfect sense thanks