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JavaScript

Posted by Max van den Berge
Max van den Berge
6,506 Points

When using querySelector(`h1`) , why is it that you write h1 as a string, and not just h1 ?

When using querySelector( h1 ) , why is it that you write h1 as a string, and not just h1 ?

  • so why this querySelector(h1) //querySelector Open parenthesis ( single quote ' h1 single quote ' ) Close parenthesis
  • instead of querySelector( h1 ) // whitout the single qoutes

is there a rule or reason behind writing it as a string, although it is not a string?

love to hear from you!

2 Answers

Steven Parker
Steven Parker
231,264 Points
Steven Parker
Steven Parker
231,264 Points

Putting quotes around something defines it as a string literal, which is a string. The argument to querySelector will always be a string that contains a CSS-style selector. In this case, the string contents "h1" indicate that the element to search for is a heading type 1.

Leaving off the quotes would cause it to be taken as a variable name, which could still work if that variable had already been created and contained an appropriate string. For example:

let heading = document.querySelector('h1');

// the above will do the same thing as this:
let h1 = 'h1';
let heading = document.querySelector(h1);

// the variable name is not important, so this also would do the same thing:
let selector = 'h1';
let heading = document.querySelector(selector);
Richard Tillies
STAFF
Richard Tillies
Treehouse Teacher
Richard Tillies
Richard Tillies
Treehouse Teacher

Hi Max - the argument for querySelector() is a String, although most parsers are smart enough to interpret h1 (without quotes) as a String, similar to how you can normally omit quotes for most HTML tags in most cases.

Here's an example where you DO need quotes: querySelector('h2, h3') Without the quotes, this will not parse correctly and the output will likely be incorrect (if it processes at all).

Hope this helps!

Max van den Berge
Max van den Berge
6,506 Points

oke, thanks!

Steven Parker
Steven Parker
231,264 Points
Steven Parker
Steven Parker
231,264 Points

I was a bit shocked to read where you said "...although most parsers are smart enough to interpret h1 (without quotes) as a String,"

All JavaScript engines that I'm aware of would interpret h1 (without quotes) as a variable name, and not a string.