I have repeated JS code, how do I turns these into functions

Here is the JSFiddle link for my project, you can see the full app.js here... http://ift.tt/2Dfvjmh

Basically I am trying to build a contact diary where you create new contacts and then be able to edit or delete them at a later stage...

on line 85 onwards is the click event for the Edit and Delete buttons, I have got these buttons working to some extent however I know that the way I have written this part of the code is incorrect because I have repeated loops and if statements.

I have tried putting these repeated parts of the code into functions but then the app crashes and I receive different errors ie:- so and so is not defined, functions not returning the correct value etc. I have tried a couple of things to overcome these errors but still cant get it to work and or get my head around this.

Please could you show/tell me how to make this code better in terms of DRY, and readability. Thank you.

Here is the part of the code in question -

//Click event for Edit and Delete buttons.
contacts.addEventListener("click", (e) => {

  if (e.target.tagName === "BUTTON") {
    const button = e.target;
    const ul = button.parentNode;
    if (button.textContent === "Edit") {
      for (var i = 0; i < contactsBook.length; i++) {
        if (contactsBook[i].firstName === ul.getAttribute('data-person')) {
          const ulChild = ul.childNodes;
          for (var j = 0; j < ulChild.length; j++) {
            if (ulChild[j].tagName === "LI") {
              const items = ulChild[j];
              const input = document.createElement('input');
              input.type = 'text';
              input.value = items.textContent;
              items.textContent = "";
              items.insertBefore(input, ulChild.childNodes);
              button.textContent = 'Save';
            };
          };
        };
      };
    } else if (button.textContent === "Save") {
      for (var i = 0; i < contactsBook.length; i++) {
        if (contactsBook[i].firstName === ul.getAttribute('data-person')) {
          const ulChild = ul.childNodes;
          for (var j = 0; j < ulChild.length; j++) {
            if (ulChild[j].tagName === "LI") {
              console.log(ulChild[j]);
            };
          };
        };
      };
    } else if (button.textContent === "Delete") {
      contacts.removeChild(ul);
      for (var i = 0; i < contactsBook.length; i++) {
        if (contactsBook[i].firstName === ul.getAttribute('data-person')) {
          contactsBook.splice(i,1);
          localStorage.setItem('addbook', JSON.stringify(contactsBook));
        };
      };
    };
  };
});

Thank you for your help!