您可以扩展 String 原型;

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;

... and use it like this;

"Hello".distance("H");

在这里查看JSFiddle 。