Show The Class If Its Not Visible ,or Hide It If It Is Visible?

I have the following code that don't work like i want it.

Code:
function hideDisplaySingleSuite(textstring) {
var myclass1 = new RegExp('\b'+textstring+'\b');
//Populate the array with all the page tags[code]....

For example.It show objects if I remove the if statement that checks if the class is visible.for example this shows a class and works.

Code:
function hideDisplaySingleSuite(textstring) {
var myclass1 = new RegExp('\b'+textstring+'\b');
//Populate the array with all the page tags[code]....

So my question is why don't this work on a class, it works on an "id"?

Code:
if (allPageTags[i].style.display ==''){
allPageTags[i].style.display = 'none';
}[code]....

I want to show the class if its not visible or hide it if it is visible.How can this be done?