Function isPromise

test/jasmine/tests/toimage_test.js:60–62

(x)

    it('should return a promise', function (done) {
        function isPromise(x) {
            return !!x.then && typeof x.then === 'function';
        }

        var returnValue = Plotly.newPlot(gd, subplotMock.data, subplotMock.layout).then(Plotly.toImage);