allow several build() calls for hot module replacement, fix #7

Author: vitalets

src/__tests__/api.test.js

@@ -72,9 +72,15 @@ describe('EStyleSheet API', function () {
     });
   });
 
-  it('should throw error on second `build` call', function () {
-    api.build();
-    expect(() => api.build()).toThrowError('No need to call `EStyleSheet.build()` more than once');
+  it('should work correctly with several `build()` calls', function () {
+    const res1 = api.create({$b: '$a'});
+    api.build({a: 1});
+    const res2 = api.create({$b: '$a'});
+    expect(res1).toEqual({$b: 1});
+    expect(res2).toEqual({$b: 1});
+    api.build({a: 2});
+    expect(res1).toEqual({$b: 2});
+    expect(res2).toEqual({$b: 2});
   });
 
   it('should calculate value', function () {

src/api.js

@@ -34,9 +34,8 @@ export default class {
     let sheet = new Sheet(obj);
     if (this.builded) {
       sheet.calc(this.globalVars);
-    } else {
-      this.sheets.push(sheet);
     }
+    this.sheets.push(sheet);
     return sheet.getResult();
   }
 
@@ -45,11 +44,7 @@ export default class {
    * @param {Object} [gVars]
    */
   build(gVars) {
-    if (this.builded) {
-      throw new Error('No need to call `EStyleSheet.build()` more than once');
-    } else {
-      this.builded = true;
-    }
+    this.builded = true;
     this._calcVars(gVars);
     this._calcSheets();
     this._callListeners(BUILD_EVENT);
@@ -95,13 +90,11 @@ export default class {
 
   _calcSheets() {
     this.sheets.forEach(sheet => sheet.calc(this.globalVars));
-    this.sheets.length = 0;
   }
 
   _callListeners(event) {
-    if (this.listeners[event]) {
+    if (Array.isArray(this.listeners[event])) {
       this.listeners[event].forEach(listener => listener());
-      delete this.listeners[event];
     }
   }
 }