The at() method of String values takes an integer value and returns a new String consisting of the single UTF-16 code unit located at the specified offset. This method allows for positive and negative integers. Negative integers count back from the last string character.
Syntax
at(index)
Parameters
index- : The index (position) of the string character to be returned. Supports relative indexing from the end of the string when passed a negative index; i.e. if a negative number is used, the character returned will be found by counting back from the end of the string.
Return value
A String consisting of the single UTF-16 code unit located at the specified position. Returns undefined if the given index can not be found.
Examples
Return the last character of a string
The following example provides a function which returns the last character found in a specified string.
// A function which returns the last character of a given string
function returnLast(arr) {
return arr.at(-1);
}
let invoiceRef = "myinvoice01";
console.log(returnLast(invoiceRef)); // '1'
invoiceRef = "myinvoice02";
console.log(returnLast(invoiceRef)); // '2'
Comparing methods
Here we compare different ways to select the penultimate (last but one) character of a String. Whilst all below methods are valid, it highlights the succinctness and readability of the at() method.
const myString = "Every green bus drives fast.";
// Using length property and charAt() method
const lengthWay = myString.charAt(myString.length - 2);
console.log(lengthWay); // 't'
// Using slice() method
const sliceWay = myString.slice(-2, -1);
console.log(sliceWay); // 't'
// Using at() method
const atWay = myString.at(-2);
console.log(atWay); // 't'