将方法添加到字符串类

您可以扩展

String

String.prototype.distance = function (char) {    var index = this.indexOf(char);    if (index === -1) {        alert(char + " does not appear in " + this);    } else {        alert(char + " is " + (this.length - index) + " characters from the end of the string!");    }};

…并像这样使用它；

"Hello".distance("H");