How to remove items from list that were pushed-CodePudding

I am trying to remove only items that were pushed into a list so that I am only left with the original list items

const list = ["a", "b", "c", "d"];

for (let i = 0; i < 4; i  ) {
  list.push(i);
}

console.log(list);

// outputs: a,b,c,d,1,2,3,4 // as expected

// how can we remove only the pushed items.
list.pop;
console.log(list);

// outputs : []

// desired output: a,b,c,d

CodePudding user response：

I'm not sure what your case is and why you want to extract the items from the array but anyway.
The first option would be: duplicating the array into another variable
or the second option: extracting it using splice when you know the length of the original array.

Snippets:

const list = ["a", "b", "c", "d"];
const original = list.slice(); // duplicating array

const originalLength = list.length // getting original length

for (let i = 0; i < 4; i  ) {
  list.push(i);
}

console.log("original1: ", original);
console.log("original2: ", list.slice(0, originalLength));

CodePudding user response：

You can remove the elements from the index where you have begun pushing new elements using splice.

const list = ["a", "b", "c", "d"];

for (let i = 0; i < 4; i  ) {
  list.push(i);
}

list.splice(list.length - 4)
console.log(list);

CodePudding user response：

If you need two to have one "for loop" pushing items into an array, and then remove those same items in another loop, then a simple solution would be

Snippet:

const list = ["a", "b", "c", "d"];

for (let i = 0; i < 4; i  ) {
  list.push(i);
}

for (let j of list) {
  if (j) {
    list.pop();
  }
};
console.log(list);