2nd block never gets executed in exercise CP_03_02

[rkkarn32]

Below code section will never get executed. object x is of type string (Which is literal), and we are checking for instance String (Which is interface).

if(x instanceof String) {
        x.substr(0)
}

See below sample code

function totalLength(x: string, y: string): number
function totalLength(x: any[], y: any[]): number
function totalLength(x: (string | any[]), y: (string | any[])): number {
    var total: number = x.length + y.length;    
    if(x instanceof Array) {
        x.push('TypeScript')
    }   
    if(x instanceof String) {
        x = x.substr(1,3);
    }
    console.log(x)
    return total;
}
totalLength("first","second");

Expected output: eco
Actual output: first