ES6: Array Slice — Must Know Usage

Arrays are list-like objects whose prototype has methods to perform traversal and mutations. Neither the length of JavaScript array nor their elements are fixed. Array are widely used in web applications, below will explain most widely used prototype method Slice. Most of the tricky questions or algorithms asked will make use of Slice methods. They plays important roles in Functional Programming.

Important things about Slice Method:

• It returns the shallow copy of a portation of an Array into a new array object. Original array will not be modified.
• Object references are copied into the new array. Both the original and new array refer to the same object.
• For strings, numbers and booleans (not String, Number, Boolean objects), it copies the values. So changes in one array do not affect the other array.

Caution: The slice method is not to be confused with the splice method, which modifies an array in place.

Syntax Slice

arr.slice(begin[, end]])

• Both arguments are optional
• When provided negative indices, counts back from the end of array.

For more details about how it works refer MDN Documentations

Interview Tips

• Write a function which will rotate the characters of given string, left and then right sequentially,
  for example
  getShiftedString(string, shiftLeft, shiftRight)
  Input: getShiftedString(“UnitedWeStand”, 2, 1)
  OutPut: nitedWeStandU

function getShiftedString(s, leftShifts, rightShifts) {

const arr = […s];

const netLeftShifts = (leftShifts — rightShifts) % arr.length;

return […arr.slice(netLeftShifts), …arr.slice(0, netLeftShifts)] .join(‘’);

}

console.log(getShiftedString(“UnitedWeStand”, 2, 1));