Here is a simple tip to check all checkboxes in a page. I found this particularly useful in granting FLS permission to a profile.
Go to your profile > Object Settings > The object you want to add FLS to & click on edit button,
Open Developer Console. If you are using Google Chrome, it is available in Menu > More tools > Developer Console
Enter the following code snippet in the Console and hit enter,
[code language=\”javascript\”]
var all = document.getElementsByTagName(\”input\”)
for(var a in all) if(all[a].type == \’checkbox\’) all[a].checked = \”checked\”;
[/code]
This will check all checkboxes in the page,
Save your page.