http:// を補完する.

ttp:// とか tp:// とかを http:// にする.

function completeHttp(str) {
    var sc = "http://"
    var h = sc.split("");
    var i = 0;
    while(str.indexOf(h.join('')) != 0) {
        h.shift();
        i++;
    }
    return sc.substr(0, i) + str;
}

var a = "http://www.google.com/";
var b = "ttp://www.google.com/";
var c = "tp://www.google.com/";
var d = "p://www.google.com/";
var e = "://www.google.com/";
var f = "//www.google.com/";
var g = "/www.google.com/";
var h = "www.google.com/";

print(completeHttp(a) == a);
print(completeHttp(b) == a);
print(completeHttp(c) == a);
print(completeHttp(d) == a);
print(completeHttp(e) == a);
print(completeHttp(f) == a);
print(completeHttp(g) == a);
print(completeHttp(h) == a);

追記

普通に正規表現でできたな.トラックバックを参考.