asNumber: return undefined when value is empty string (#369)

Also

* add eslint rule for spacing

.eslintrc

@@ -15,7 +15,8 @@
         "comma-dangle": [0],
         "no-unused-vars": [2, {"vars": "all", "args": "none"}],
         "no-console": [0],
-        "object-curly-spacing": [1, "never"]
+        "object-curly-spacing": [1, "never"],
+        "keyword-spacing": ["error"]
     },
     "env": {
         "es6": true,

src/components/fields/ObjectField.js

@@ -101,7 +101,7 @@ class ObjectField extends Component {
     try {
       const properties = Object.keys(schema.properties);
       orderedProperties = orderProperties(properties, uiSchema["ui:order"]);
-    } catch(err) {
+    } catch (err) {
       return (
         <div>
           <p className="config-error" style={{color: "red"}}>

src/utils.js

@@ -223,6 +223,9 @@ export function mergeObjects(obj1, obj2, concatArrays = false) {
 }
 
 export function asNumber(value) {
+  if (value === "") {
+    return undefined;
+  }
   if (/\.$/.test(value)) {
     // "3." can't really be considered a number even if it parses in js. The
     // user is most likely entering a float.
@@ -500,7 +503,7 @@ export function dataURItoBlob(dataURI) {
   // Built the Uint8Array Blob parameter from the base64 string.
   const binary = atob(splitted[1]);
   const array = [];
-  for(let i = 0; i < binary.length; i++) {
+  for (let i = 0; i < binary.length; i++) {
     array.push(binary.charCodeAt(i));
   }
   // Create the blob object

test/ArrayField_test.js

@@ -189,7 +189,7 @@ describe("ArrayField", () => {
 
       try {
         Simulate.submit(node);
-      } catch(e) {
+      } catch (e) {
         // Silencing error thrown as failure is expected here
       }
 

test/FormContext_test.js

@@ -60,7 +60,7 @@ describe("FormContext", () => {
 
   it("should be passed to TemplateField", () => {
     function CustomTemplateField({formContext}) {
-      return <div id={formContext.foo} />;
+      return <div id={formContext.foo}/>;
     }
 
     const {node} = createFormComponent({

test/Form_test.js

@@ -634,7 +634,7 @@ describe("Form", () => {
           function submit(node) {
             try {
               Simulate.submit(node);
-            } catch(err) {
+            } catch (err) {
               // Validation is expected to fail and call console.error, which is
               // stubbed to actually throw in createSandbox().
             }

test/utils_test.js

@@ -255,6 +255,10 @@ describe("utils", () => {
     it("should allow numbers with a 0 in the first decimal place", () => {
       expect(asNumber("3.07")).eql(3.07);
     });
+
+    it("should return undefined if the input is empty", () => {
+      expect(asNumber("")).eql(undefined);
+    });
   });
 
   describe("isMultiSelect()", () => {