JSFiddle - React, Tailwind, and code Playground

JavaScript

String.prototype.strim = function(needle)   {
    var out = this;
    while (0 === out.indexOf(needle))
        out = out.substr(needle.length);
    while (out.length === out.lastIndexOf(needle) + needle.length)
        out = out.slice(0,out.length-needle.length);
    return out;
}

var spam = "this is a string. this ends with thisthis";
alert("#" + spam.strim("this") + "#");