How to update a string in embedded string array?

[Son Truong]

Hello,

I have a problem with embedded string array. I have a schema:

new mongoose.Schema({
      im : [String] //[ "image link 1", "image link 2", "image link 3", "image link 4", "image link 5"]

}

I push full 5 images, now I want update a new image link string base on old one. How can I do that? 

Thank you.