尝试添加和删除数组中的项目

Question

The script works by asking user for add or remove an item in the array. Then asks to continue this loop. The problem here is that my script doesn't seem to match my user's input (removeItem) to the item in the list (myList[i]). I'm at a lost as to why this is failing to match.

// new method for removing specific items from a list
Array.prototype.remove = function(from,to) {
    var rest = this.slice((to || from) + 1 || this.length);
    this.length = from < 0 ? this.length + from : from;
    return this.push.apply(this, rest);
};

printList = function() {
    var listLength = myList.length;
    for (i = 0; i < listLength; i++) {
        document.write(i + ":");
        document.write(myList[i] + "<br/>");
    };
    document.write("<br/><br/>");
};

// initial list
var myList = new Array ();
if (myList.length === 0) {
    document.write("I have " + myList.length + " item in my list. It is: <br/>");
}
else {
    document.write("I have " + myList.length + " items in my list. They are: <br/>");
}
printList();

var continueAdding = "yes";
var askToContinue = "";

while (continueAdding === "yes") {
    // loop
    var askUser = prompt("What do you want to [A]dd or [R]emove an item to your inventory?").toUpperCase();
    switch (askUser) {
        case "A": { // add an user specified item to the list
            var addItem = prompt("Add something to the list");
            myList.push(addItem);
            printList();
            break;
        }
        case "R": { // remove an user specified item from the list
            var removeItem = prompt("what do you want to remove?"); 
            var listLength = myList.length;
            for (i = 0; i < listLength; i++) {
                if (removeItem === myList[i]) {
                    document.write("I found your " + removeItem + " and removed it.<br/>");
                    myList.remove(i);
                }
                else {
                    document.write(removeItem + " does not exist in this list.<br/>");
                    break;
                }
                if (myList.length === 0) {
                    myList[0] = "Nada";
                }
            };
            printList();
            break;
        }
        default: {
            document.write("That is not a proper choice.");
        }
    };

    askToContinue = prompt("Do you wish to continue? [Y]es or [N]o?").toUpperCase(); // ask to continue
    if (askToContinue === "Y") {
        continueAdding = "yes";
    }
    else {
        continueAdding = "no";
    }
}

Answer 1

Your loop never allows it to loop through all the items, because it breaks on the first iteration if the item doesn't match.

The break statement should be in the if block, not in the else block - use this instead:

for (i = 0; i < listLength; i++) {
    if (removeItem === myList[i]) {
        document.write("I found your " + removeItem + " and removed it.<br/>");
        myList.remove(i);
        break;
    }
    else {
        document.write(removeItem + " does not exist in this list.<br/>");
    }
};

if (myList.length === 0) {
    myList[0] = "Nada";
}

Also, note that it's looking for an exact match, case sensitive, same punctuation, and everything. If you want it to be a little more lenient you'll need to modify the script to convert both strings to lowercase and strip punctuation before comparing them.

Edit: Just noticed something else -- testing for an empty list needs to be done outside the loop. I updated the above code to reflect this.