Cacher is the code snippet organizer for pro developers

var str = "btn  list-share  btn-share-option send-to-friend share-option list-title print-page content-header item-list wishlist-item-list headings item-image item-details item-availablity item-actions wishlist-item-td item-availability item-dashboard item-option option-date-added label value option-quantity-desired  option-priority option-toggle-public option-update button-text button-link option-add-to-cart  item-option-btn btn-long";
var arr = str.split(" ");
var result = [];


for(var i = 0; i < arr.length; i++) {
    if(arr[i].indexOf("btn") === 0) {
        result.push(arr[i]);
    }
}


console.log(result);