Comment by mirekrusin

11 years ago

Edge case for left padding - when you provide empty string as padding filler. It can go into infinite loop if not written correctly.

Write a damn unit test for your padding function. We should share unit tests, not one-line libs. Libs with unit tests can be one-liners and be as fine-grained as we like, since it's something your users don't have to download

  • > We should share unit tests, not one-line libs.

    Most of the small libs I've shared are mainly sharing unit tests.

    Here's a function I've shared on npm:

      var kind = function(item) {
        var getPrototype = function(item) {
          return Object.prototype.toString.call(item).slice(8, -1);
        };
        var kind, Undefined;
        if (item === null ) {
          kind = 'null';
        } else {
          if ( item === Undefined ) {
            kind = 'undefined';
          } else {
            var prototype = getPrototype(item);
            if ( ( prototype === 'Number' ) && isNaN(item) ) {
              kind = 'NaN';
            } else {
              kind = prototype;
            }
          }
        }
        return kind;
      };
    

    The tests:

      suite('kind', function(){
        test('shows number-like things as numbers', function(){
          assert(avkind(37) === 'Number');
          assert(avkind(3.14) === 'Number');
          assert(avkind(Math.LN2) === 'Number');
          assert(avkind(Infinity) === 'Number');
          assert(avkind(Number(1)) === 'Number');
          assert(avkind(new Number(1)) === 'Number');
        });
        test('shows NaN as NaN', function(){
          assert(avkind(NaN) === 'NaN');
        });
        test('Shows strings as strings', function(){
          assert(avkind('') === 'String');
          assert(avkind('bla') === 'String');
          assert(avkind(String("abc")) === 'String');
          assert(avkind(new String("abc")) === 'String');
        });
        test('shows strings accurately', function(){
          assert(avkind(true) === 'Boolean');
          assert(avkind(false) === 'Boolean');
          assert(avkind(new Boolean(true)) === 'Boolean');
        });
        test('shows arrays accurately', function(){
          assert(avkind([1, 2, 4]) === 'Array');
          assert(avkind(new Array(1, 2, 3)) === 'Array');
        });
        test('shows objects accurately', function(){
          assert(avkind({a:1}) === 'Object');
          assert(avkind(new Object()) === 'Object');
        });
        test('shows dates accurately', function(){
          assert(avkind(new Date()) === 'Date');
        });
        test('loves Functions too', function(){
          assert(avkind(function(){}) === 'Function');
          assert(avkind(new Function("console.log(arguments)")) === 'Function');
          assert(avkind(Math.sin) === 'Function');
        });
        test('shows undefined accurately', function(){
          assert(avkind(undefined) === 'undefined');
        });
        test('shows null accurately', function(){
          assert(avkind(null) === 'null');
        });
      });

If you've called it with an empty string there's probably a bug in your calling code which you'll want to test for anyway.