查找字符串数组中是否已经存在字符串-javascript

Question

I have an array called blog.likes and i want to check to see if the id of the current logged in user(req.user._id) already exists inside the array of likes. If it does then delete the id from the array if it doesn't then add the user id inside the array. With the code i have now if i press the like button once it likes the post if i press it again it removes the like but if a post has a like and i log in with a different user and press the like button many times it starts to delete all the likes not only the likes that are made by one user.

         if (blog.likes.indexOf(req.user._id) > -1 ){
             blog.likes.shift(req.user._id);
             blog.save();
           } else {
          blog.likes.push(req.user);
           blog.save();
          }

Answer 1

The shift function will only remove the first element from the array, paying no heed to the logged in user id. Use splice function to achieve the desired result. Change your code to this:

let userIndex = blog.likes.indexOf(req.user._id);
if (userIndex > -1) {
  blog.likes.splice(userIndex, 1);
} else {
  blog.likes.push(req.user);
}
blog.save();

Answer 2

As I mentioned in the comments .shift() is not the correct method to use. Give this a try:

var f = blog.likes.indexOf(req.user._id);
if (f > -1 ) {
  blog.likes.splice(f, 1);
} else {
  blog.likes.push(req.user);
}
blog.save();