enable prefer-const rule for tslint, fix issues (#4409)

* enable prefer-const rule for tslint, fix issues

* Update content-node-selector.component.spec.ts

* Update content-node-selector.component.spec.ts

* fix const

* fix lint issues

* update tests

* update tests

* update tests

* fix code

* fix page class

lib/core/utils/file-utils.ts

@@ -24,10 +24,10 @@ export interface FileInfo {
 export class FileUtils {
 
     static flatten(folder: any): Promise<FileInfo[]> {
-        let reader = folder.createReader();
-        let files: FileInfo[] = [];
+        const reader = folder.createReader();
+        const files: FileInfo[] = [];
         return new Promise((resolve) => {
-            let iterations = [];
+            const iterations = [];
             (function traverse() {
                 reader.readEntries((entries) => {
                     if (!entries.length) {
@@ -60,7 +60,7 @@ export class FileUtils {
     }
 
     static toFileArray(fileList: FileList): File[] {
-        let result = [];
+        const result = [];
 
         if (fileList && fileList.length > 0) {
             for (let i = 0; i < fileList.length; i++) {

lib/core/utils/momentDateAdapter.ts

@@ -89,7 +89,7 @@ export class MomentDateAdapter extends DateAdapter<Moment> {
     }
 
     clone(date: Moment): Moment {
-        let locale = this.locale || 'en';
+        const locale = this.locale || 'en';
         return date.clone().locale(locale);
     }
 
@@ -98,12 +98,12 @@ export class MomentDateAdapter extends DateAdapter<Moment> {
     }
 
     today(): Moment {
-        let locale = this.locale || 'en';
+        const locale = this.locale || 'en';
         return moment().locale(locale);
     }
 
     parse(value: any, parseFormat: any): Moment {
-        let locale = this.locale || 'en';
+        const locale = this.locale || 'en';
 
         if (value && typeof value === 'string') {
             let m = moment(value, parseFormat, locale, true);
@@ -207,8 +207,8 @@ export class MomentDateAdapter extends DateAdapter<Moment> {
     }
 
     fromIso8601(iso8601String: string): Moment | null {
-        let locale = this.locale || 'en';
-        let d = moment(iso8601String, moment.ISO_8601).locale(locale);
+        const locale = this.locale || 'en';
+        const d = moment(iso8601String, moment.ISO_8601).locale(locale);
         return this.isValid(d) ? d : null;
     }
 

lib/core/utils/object-utils.spec.ts

@@ -20,19 +20,19 @@ import { ObjectUtils } from './object-utils';
 describe('ObjectUtils', () => {
 
     it('should get top level property value', () => {
-        let obj = {
+        const obj = {
             id: 1
         };
         expect(ObjectUtils.getValue(obj, 'id')).toBe(1);
     });
 
     it('should not get top level property value', () => {
-        let obj = {};
+        const obj = {};
         expect(ObjectUtils.getValue(obj, 'missing')).toBeUndefined();
     });
 
     it('should get nested property value', () => {
-        let obj = {
+        const obj = {
             name: {
                 firstName: 'John',
                 lastName: 'Doe'
@@ -43,7 +43,7 @@ describe('ObjectUtils', () => {
     });
 
     it('should not get nested property value', () => {
-        let obj = {};
+        const obj = {};
         expect(ObjectUtils.getValue(obj, 'some.missing.property')).toBeUndefined();
     });
 

lib/core/utils/object-utils.ts

@@ -28,12 +28,12 @@ export class ObjectUtils {
             return undefined;
         }
 
-        let keys = key.split('.');
+        const keys = key.split('.');
         key = '';
 
         do {
             key += keys.shift();
-            let value = target[key];
+            const value = target[key];
             if (value !== undefined && (typeof value === 'object' || !keys.length)) {
                 target = value;
                 key = '';
@@ -48,7 +48,7 @@ export class ObjectUtils {
     }
 
     static merge(...objects): any {
-        let result = {};
+        const result = {};
 
         objects.forEach((source) => {
             Object.keys(source).forEach((prop) => {