make expression(a, b) resolve to a = b

expression.js

@@ -56,6 +56,10 @@ var Expression = function(field, op, value)
     } else {
       left = `${escape(field, true)}`;
     }
+    if(value === undefined) {
+      value = op;
+      op = 'eq';
+    }
     if(value instanceof Expression) {
       right = `(${value.toString()})`;
     } else {

spec/expression_spec.js

@@ -32,6 +32,10 @@ describe('expression tests', function() {
     expect(new Expression(e2, '=', e3).toString()).toEqual('(b add 2) eq (5)');
   });
 
+  it('should express e2 = e3, method 2', function() {
+    expect(new Expression(e2, e3).toString()).toEqual('(b add 2) eq (5)');
+  });
+
   it('should express e2 != e3', function() {
     expect(new Expression(e2, '!=', e3).toString()).toEqual('(b add 2) ne (5)');
   });

spec/filter_spec.js

@@ -34,7 +34,7 @@ describe('filter tests', function() {
   });
 
  it('should produce a filter credit > 5000 and (balance = 0 or status = \'stop\')', function() {
-   expect(odata.filter('credit', '>', 5000).and(Odata.expression('balance', '=', 0).or('status', '=', 'stop')).query())
+   expect(odata.filter('credit', '>', 5000).and(Odata.expression('balance', 0).or('status', 'stop')).query())
       .toEqual('https://example.com/Customer?%24filter=(credit%20gt%205000)%20and%20((balance%20eq%200)' +
                '%20or%20(status%20eq%20\'stop\'))');
   });
@@ -45,7 +45,7 @@ describe('filter tests', function() {
   });
 
   it('should produce a filter \'ABC001\' eq account', function() {
-    expect(odata.filter(Odata.literal('ABC001'), '=', Odata.identifier('account')).query())
+    expect(odata.filter(Odata.literal('ABC001'), Odata.identifier('account')).query())
       .toEqual('https://example.com/Customer?%24filter=\'ABC001\'%20eq%20account');
   });