Introduce starts_with query filter

Author: Lance Welsh

lib/query.js

@@ -12,7 +12,9 @@ module.exports = (function() {
     'ilike': function(a, b) { return a.toLowerCase().indexOf(b.toLowerCase()) > -1; },
     'like': function(a, b) { return a.indexOf(b) > -1; },
     'in': function(a, b) { return b.indexOf(a) > -1; },
-    'not_in': function(a, b) { return b.indexOf(a) === -1; }
+    'not_in': function(a, b) { return b.indexOf(a) === -1; },
+    'starts_with': function(a, b) { const re = new RegExp('^' + b, ''); return !!a.match(re); },
+    'istarts_with': function(a, b) { const re = new RegExp('^' + b, 'i'); return !!a.match(re); }
   };
 
   class Query {

test/runner.js

@@ -394,6 +394,28 @@ describe('Test Suite', function() {
 
         });
 
+        it('should filter starts_with', function() {
+
+          expect(nc.query().filter({name__starts_with: 'Keith'}).units().length).to.equal(1);
+          expect(nc.query().filter({name__starts_with: 'Keith'}).first()).to.equal(nc.find(1));
+
+          expect(nc.query().filter({name__starts_with: 'K'}).units().length).to.equal(2);
+          expect(nc.query().filter({name__starts_with: 'K'}).first()).to.equal(nc.find(1));
+          expect(nc.query().filter({name__starts_with: 'K'}).units()[1]).to.equal(nc.find(4));
+
+        });
+
+        it('should filter istarts_with', function() {
+
+          expect(nc.query().filter({name__istarts_with: 'keith'}).units().length).to.equal(1);
+          expect(nc.query().filter({name__istarts_with: 'keith'}).first()).to.equal(nc.find(1));
+
+          expect(nc.query().filter({name__istarts_with: 'k'}).units().length).to.equal(2);
+          expect(nc.query().filter({name__istarts_with: 'k'}).first()).to.equal(nc.find(1));
+          expect(nc.query().filter({name__istarts_with: 'k'}).units()[1]).to.equal(nc.find(4));
+
+        });
+
         it('should exclude as expected', function() {
 
           expect(nc.query().exclude({name__is: 'Keith'}).first()).to.equal(nc.find(2));