How to clone array in ES6 ?
The spread operator in ES6 is used to clone an array, whereas slice() method in JavaScript is an older way that provide 0 as the first argument. These methods create a new, independent array and copy all the elements of oldArray to the new one i.e. both these methods do a shallow copy of the original array.
Syntax:
// Older way var clonedArray= oldArray.slice(0) // ES6 way: spread operator var clonedArrayES6= [...oldArray]
Example:
<script> // Cloning array using spread// operator- ES6 const oldArray= ["dog1", "dog2", "dog3"]; const clonedArrayES6= [...oldArray]; // ["dog1", "dog2", "dog3"]console.log(clonedArrayES6); </script> |
Output:
Equality and sameness: Unlike “=” operator, which creates a new variable which just points to the original array instead of copying its elements, spread operator creates a new, cloned array, with different reference but same values. Hence “=” operator creates a deep copy of the original array but the spread operator does a shallow copy. The array created by the spread operator has the same value as that of the old array but, is not as same as the old array.
Example:
<script>// Equality and sameness in cloning array const oldArray= ["dog1", "dog2", "dog3"]; const clonedArrayES6 = [...oldArray];const newArray = oldArray; // False, i.e. shallow copyconsole.log(clonedArrayES6===oldArray) // True, i.e. deep copyconsole.log(newArray === oldArray) </script> |
Output:
Note: All the above examples can be tested by typing them within the script tag of HTML or directly into the browser’s console.
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