src/lib/utils/Str.js
function at(index) {

    if (!this) {
        throw TypeError();
    }

    const str = '' + this,
        len = str.length;

    if (index >= len) {
        return;
    }
    if (index < 0) {
        index = len - index;
    }

    let i = 0;
    for (let item of str) {
        if (i === index) {
            return item;
        }
    }

    return;

}
function at(index) {

    if (!this) {
        throw TypeError();
    }

    const str = '' + this,
        len = str.length;

    if (index >= len) {
        return;
    }
    if (index < 0) {
        index = len - index;
    }

    let i = 0;
    for (let item of str) {
        if (i === index) {
            return item;
        }
    }

    return;

}
function at ( index ) { if ( ! this ) { throw TypeError ( ) ; } const str = '' + this , len = str . length ; if ( index >= len ) { return ; } if ( index < 0 ) { index = len - index ; } let i = 0 ; for ( let item of str ) { if ( i === index ) { return item ; } } return ; }
String.at polyfill
@param index
@returns {*}
String . at polyfill