javascript - lastindexof and substring js confusion in my case -

i try id value in path using js below code:

var path = 'http://storecoupon.in/store/amazon-promo-codes/?id=212'; var n = path.lastindexof('/');  var getparams = path.substring(n+5, path.length); console.log(getparams); 

why console display blank?

here's nice approach found in https://gist.github.com/jlong/2428561 parse url:

var parser = document.createelement('a'); parser.href = "http://example.com:3000/pathname/?search=test#hash";  parser.protocol; // => "http:" parser.hostname; // => "example.com" parser.port;     // => "3000" parser.pathname; // => "/pathname/" parser.search;   // => "?search=test" parser.hash;     // => "#hash" parser.host;     // => "example.com:3000" 

further can fetch parameters search this:

// if i'm not mistaken, search doesn't contain "?" prefix in browsers var search = parser.search.replace(/^\?/, ''); var params = search.split('&'); var map = {}; (var = 0; < params.length; i++) {   var param = params[i].split('=');   map[param[0]] = param[1]; } // map['id'] need 

still might easier use javascript library "js-url", see https://github.com/websanova/js-url.

// return "212" url('?id', 'http://storecoupon.in/store/amazon-promo-codes/?id=212');