Select All checkbox by Javascript or console

querySelectorAll is your best choice here if you don't want jQuery!

var ele = document.querySelectorAll("input[type=checkbox]");
for(var i=0;i<ele.length;i++){
    ele[i].checked = true;
}
//Done.

by using jquery, simple as that

$('input:checkbox').each(function () {
   // alert(this);
   $(this).attr('checked', true);
  });

Or simply use

$('input:checkbox').prop('checked', true);// use the property

OR

 $('input:checkbox').attr('checked', true); // by using the attribute

The most direct way would be to grab all your inputs, filter just the checkboxes out, and set the checked property.

var allInputs = document.getElementsByTagName("input");
for (var i = 0, max = allInputs.length; i < max; i++){
    if (allInputs[i].type === 'checkbox')
        allInputs[i].checked = true;
}

---

If you happen to be using jQuery—and I'm not saying you should start just to tick all your checkboxes for testing—you could simply do

$("input[type='checkbox']").prop("checked", true);

or as Fabricio points out:

$(":checkbox").prop("checked", true);

Pure JS method, don't use jQuery.. its just silly for something so trivial.

[].forEach.call( document.querySelectorAll('input[type="checkbox"]'),function(el){
       el.checked=true;
     }
);​

Live Demo

To use it on any webpage you can paste this into the address bar

javascript:[].forEach.call(document.querySelectorAll('input[type="checkbox"]'),function(el){el.checked=true});

then drag that to your bookmarks, and you have a bookmarklet. Just click it whenever you need to use it on a page.