Copy substring of string array into new array in Javascript

Question

I am looking to copy the substring of a string array into a new array without creating references. This is giving me a headache yet this should be fairly simple.

I tried NewArray[n] = OldArray[n].substr(x,y).slice(0) inside a loop and does not work. (I need to do a NewArray.sort() afterwards).

For the sake of example, say I got an OldArray with 2 elements:

['River', 'Lake']

I want the new array to be made of the first 2 characters (substring) of the old one such that:

['Ri', 'La']

Answer 1

copy the substring of a string array into a new array without creating references

Strings are primitive values in JavaScript, not Objects. There will be no reference when assigning the values of the old into the new array, especially when creating new strings with substr. The slice(0) you've used is superfluous when used with strings, and not necessary on arrays in your case, too.

Your code should work:

var oldArray = ["River", "Lake"];

var newArray = [];
for (var i=0; i<oldArray.length; i++)
   newArray[i] = oldArray[i].substr(0,2);

// newArray: ["Ri", "La"]

Answer 2

This worked for me. Thanks @Bergi

const newArray = oldArray.map( str => str.substr(0,2) );