Remove last item from array
Array.prototype.pop() by JavaScript convention.
let fruit = ['apple', 'orange', 'banana', 'tomato'];let popped = fruit.pop();console.log(popped); // "tomato"console.log(fruit); // ["apple", "orange", "banana"]
You can do this using .slice() method like:
arr.slice(0, -1); // returns [1,0]Here is a demo:
var arr = [1, 0, 2];var newArr = arr.slice(0, -1); // returns [1,0]console.log(newArr);$('#div1').text('[' + arr + ']');$('#div2').text('[' + newArr + ']');<script src="http://code.jquery.com/jquery.min.js"></script><b>Original Array : </b><div id="div1"></div><br/><b>After slice(0, -1): </b><div id="div2"></div>instead of doing :
arr.slice(-1); // returns [2]Here is a demo:
var arr = [1, 0, 2];var newArr = arr.slice(-1); // returns [2]console.log(newArr);$('#div1').text('[' + arr + ']');$('#div2').text('[' + newArr + ']');<script src="http://code.jquery.com/jquery.min.js"></script><b>Original Array : </b><div id="div1"></div><br/><b>After slice(-1): </b><div id="div2"></div>Explanation:-
Now the basic syntax of Array.prototype.slice() or in short slice() method is:
arr.slice([begin[, end]])Here,
the begin parameter is zero-based index at which extraction from an array starts. So, lets say based on above example if we do something like
arr.slice(0) // returns [1,0,2]it would return all the array elements from start of sequence from position 0 and that is [1,0,2]. Similarly, if we do
arr.slice(1) // returns [0,2]it would return [0,2] since 0 is at position 1 here and everything after that. Now, in your case you have passed a negative index i.e., -1 as the begin parameter, which indicates an offset from the end of the sequence. So, slice(-1) in your case extracts the last one array element in the sequence and that is 2 (as we have already seen in the above demo).
Now, let's talk about the end parameter in the slice() method syntax here. It is again a zero-based index at which extraction from an array ends. So, lets say we have a array like:-
var arr = [1, 0, 2, 5, 3, 9];and we want to get just the 2,5,3 elements in the array. Now, position of 2 from start of the sequence is 2 and for last element 3 it is 4. We will need to end the extraction here a position 5, as we need to get the element before that position. So, we will simply implement slice() method here like
arr.slice(2, 5) // returns [2,5,3]In your case, we have implemented -1 as the end parameter, so our code is like
arr.slice(0, -1) // returns [1,0]As a negative index, end indicates an offset from the end of the sequence. So, slice(0,-1) extracts the first element through the second-to-last element in the sequence. So, we get the desired output. We can also do like
arr.slice(0, 2) // returns [1,0]we will get the same output. But, I have used -1 here as its easier to implement even for a long array like
[0,2,3,1,2,9,3,6,3,9,1,0,2,9,0,1,1,2,3,4,7,9,1]If you just want to remove the last element, you don't want to sit & calculate the position of last 9 here and the do like arr.slice(0, 22). You can then simply implement the negative index logic here & do
arr.slice(0, -1) // same result as arr.slice(0, 22)Hope it helps!