Author: Shiva Charan Devabhaktuni

  • State Management in Angular 5.x using ngrx

    state management

    job-state.ts

    Let us assume we have a job object with the following properties.

    export interface JobState {
        id: number;
        title: string;
        company: string;
        city: string;
        state: string;
        zip: number;
    }
    

    job-state.ts

    Let us create actions classes by implementing the Action interface and then export them with type All, to avoid type mismatch errors.

    import {Action} from '@ngrx/store';
    
    import {JobState} from './job-state';
    
    export const ADDJOB = 'ADDJOB';
    export const GETJOB = 'GETJOB';
    
    export class AddJobPost implements Action {
        readonly type = ADDJOB;
    
        constructor(public payload: JobState) {
        }
    }
    
    export class GetJobPost implements Action {
        readonly type = GETJOB;
    }
    
    export type All = AddJobPost | GetJobPost;
    

    job.reducer.ts

    Now we need to create the reducer which maps the actions to the correct state.

    import * as PostActions from './job-actions';
    import {JobState} from './job-state';
    
    export type Action = PostActions.All;
    
    const emptyJobState = {
        id: null,
        title: null,
        company: null,
        city: null,
        state: null,
        zip: null,
    };
    
    const newState = (state, newData) => {
        return Object.assign({}, state, newData);
    };
    
    export function jobReducer(state: JobState = emptyJobState, action: Action) {
        switch (action.type) {
            case PostActions.ADDJOB: {
                return newState(state, action.payload);
            }
            case PostActions.GETJOB: {
                return Object.assign({}, state);
            }
            default: {
                return Object.assign({}, state);
            }
        }
    }
    

    app.component.ts

    Now we need to include the reducer in the component, that we can to make use of this functionality. Here let us consider app.component.ts

    import {Component, OnInit} from '@angular/core';
    import {Store} from '@ngrx/store';
    
    import * as PostActions from '../reducers/job-actions';
    import {JobState} from './job-state';
    import {JobStateInterface} from './job-state.interface';
    
    @Component({
        selector: 'app',
        templateUrl: './app.component.html',
        styleUrls: ['./app.component.scss']
    })
    export class AppComponent implements OnInit {
        job: Observable;
        jobs: JobState[];
    
        constructor(private store: Store) {
            this.job = store.select('job');
        }
    
     
        setJob(obj: JobState): void {
            this.store.dispatch(new PostActions.AddJobPost(obj));
        }
    
    }
    

    job-state.interface.ts

    We need to define the interface that the store uses to retrieve the state.

    import {JobState} from './job-state';
    
    export interface JobStateInterface {
        job: JobState;
    }
    

    app.module.ts

    Finally we need to add the reducer to the app.module.ts. There is a nice chrome plugin called redux dev-tools</ that comes in handy to view the current state of the application and manipulate it. You need add the StoreDevtoolsModule line as shown below, after installing and enabling the above plugin in your code.

    // ...
    import {job} from 'job.reducer';
    
    @NgModule({
    // ...
    
     imports: [
            BrowserModule,
            AppRoutingModule,
            FormsModule,
            HttpClientModule,
            StoreModule.forRoot({login: loginReducer, job: jobReducer}),
            StoreDevtoolsModule.instrument({
                maxAge: 25
            }),
    
    // ...
    })
    
    // ...
    
  • Parameterized Pipes for input search in Angular (custom filters)

    Lets say we want to filter through a list of jobs that look like the following using an Angular 4.4.5 setup.

    job-state.ts

    export interface JobState {
        id: number;
        title: string;
        company: string;
        city: string;
        state: string;
        zip: number;
    }
    

    jobs filter

    We need to create a custom pipe that takes in the search term as an input parameter for this.

    search-jobs.pipe.ts

    import {Pipe, PipeTransform} from '@angular/core';
    
    import {JobState} from './job-state';
    
    @Pipe({
        name: 'searchJobs'
    })
    export class SearchJobsPipe implements PipeTransform {
        transform(jobs: JobState[], searchText: string): any[] {
            if (!jobs) {
                return [];
            }
            if (!searchText) {
                return jobs;
            }
            searchText = searchText.toLowerCase();
            return jobs.filter(it => {
                return it.title.toLowerCase().includes(searchText) ||
                    it.company.toLowerCase().includes(searchText) || it.city.toLowerCase().includes(searchText) ||
                    it.state.toLowerCase().includes(searchText) || it.zip.toString().toLowerCase().includes(searchText);
            });
        }
    }
    

    app.module.ts

    Now add this app.module.ts to the Declarations part of NgModule, after including the AppComponent where you wish to use this.

    // ...
    
    import {AppComponent} from './app.component';
    import {SearchJobsPipe} from './search-jobs.pipe';
    
    @NgModule({
        //
         ...
    
         declarations: [ AppComponent,
                        SearchJobsPipe 
                      ],
    
        // ....
    }]
    

    app.component.ts

    Make sure you have app.component.ts that is somewhat similar to the base structure here.

    import { Component, OnInit } from '@angular/core';
    import {JobState} from './job-state';
    
    @Component({
      selector: 'app-app1',
      templateUrl: './app1.component.html',
      styleUrls: ['./app1.component.scss']
    })
    export class App1Component implements OnInit {
      jobSearch = '';
      jobs: JobState[];
    
      constructor() { }
    
      ngOnInit() {
         this.getJobs();
      }
    
      getJobs(): void {
      // Make API call here and load the jobs on success 
      // this.jobs = response.data;
      }
    
    }
    

    app.component.html

    Now add the following code into your app.component.html file or your components template.

    
    
    
    {{job.title}} - {{job.company}}
    {{job.city}}, {{job.state}} - {{job.zip}}
  • Add font awesome icons to Bootstrap 4 input

    inline search icon

    Note
    Before you run this code, make sure you have jQuery 3.x, Bootstrap 4.x, and Font Awesome 4.x in the same order.

    HTML

    CSS

    body {
      padding: 12px;
    }
    
    .search-class {
      border: none;
      background: #ffffff;
    }
    
    .icon-search {
      border: 1px solid #f2f2f2;
      border-top-left-radius: .25em;
      border-bottom-left-radius: .25em;
      border-right: none;
      padding-right: 0;
    }
    
    .input-search {
      border: 1px solid #f2f2f2;
      border-top-right-radius: .25em;
      border-bottom-right-radius: .25em;
      border-left: none;
    }
    
    .input-search:focus {
      border-color: #f2f2f2;
    }
    
    .search-class-width {
      max-width: 400px;
    }
    

    Demo

  • Empty json_encode() output in php 7.1.x

    If you have an empty json_encode() and don’t know what the hell just went wrong, then this piece of code is really helpful.

    $json = json_encode(array('message' => 'OK', 'data' => $row["description"]));
    if ($json) {
        echo $json;
    } else {
        error_log(json_last_error_msg());
    }

    If you get an error saying invalid UTF-8 characters or something similar, then all you need to do is set the character set of your database to UTF-8 in the following way.

    connect_errno) {
        echo "Failed to connect to MySQL: (" . $mysqli->connect_errno . ") " . $mysqli->connect_error;
        die();
    }
    
     var_dump($mysqli->get_charset());
    // you should see something like 'latin1'
    
     if (!$mysqli->set_charset("utf8")) {
        error_log("Error loading character set utf8: %s\n", $mysqli->error);
        exit();
    }
    
    var_dump($mysqli->get_charset());
    // you should see something like 'UTF-8'
    
    // Do your stuff here.
    
    $mysqli->close();
    
  • Check if input is a number in PHP 7.1.x

    is_int()

    The is_int() doesn’t tell you if the string is actually a number, instead it returns false.

    
    

    If you convert your string numeric into an int and then do this, only then will it work. But there is a problem with this approach, while converting string to an int, we use intval(). This converts strings to 0's.

    
    

    is_numeric()

    So the best way to find out whether a variable is an actual numeric or not is to use this php function.

    
    
  • Delete Cookies in JavaScript

    Deleting a cookie stored in a browser using JavaScript is very easy. For example if you have a cookie named token in your browser and want to delete it, all you have to do is provide the cookie name and set it to a past date. This deletes it immediately. You can take a look at cookies in chrome’s developer tools.
    Cookies

    function setCookie(name, value, days) {
      var d = new Date();
      d.setTime(d.getTime() + (days * 24 * 60 * 60 * 1000));
      var expires = 'expires=' + d.toUTCString();
      document.cookie = name + '=' + value + ';' + expires + ';path=/';
    }
    
    function deleteCookie(name) {
      document.cookie = name + '=;expires=' + new Date(1970, 0, 1).toUTCString() + ';path=/'
    }
    
    setCookie('token', 'value here', 1);
    
    deleteCookie('token');
    

    Demo

  • Add HTTP Intercepter in Angular 4

    Creating a HTTP Intercepter

    Angular V4.4.4
    We need to inherit the ‘HttpIntercepter’ class and override the ‘intercept’ method to be able to intercept all the HTTP requests you make using ‘HttpClient’.
    auth-interceptor.ts

    import {Injectable} from '@angular/core';
    import {Observable} from 'rxjs/Observable';
    // import 'rxjs/add/operator/do';
    import {HttpEvent, HttpResponse, HttpInterceptor, HttpHandler, HttpRequest} from '@angular/common/http';
     
    @Injectable()
    export class AuthInterceptor implements HttpInterceptor {
      constructor(private auth: AuthService) {}
     
      intercept(req: HttpRequest, next: HttpHandler): Observable> {
        // Clone the request as it is immutable. You can also save the original request in the following way
        // const prevReq = req.clone();
        const authReq = req.clone({headers: req.headers.set('Authorization', 'Bearer ' + getToken())});
        // or you can use the shorter version of the same.
        //const authReq = req.clone({setHeaders: {Authorization: 'Bearer ' + getToken()}});
        // Pass on the cloned request instead of the original request.
        return next.handle(authReq);
        /* you can test the above function by doing a console.log() here. For this you will need to import 'HttpResponse' and the 'do' operator.
         .do(event => {
            if (event instanceof HttpResponse) {    
              console.log(getToken());
            }
          });
       */
      }
    }

    Updating app.module.ts

    Now you need to include the ‘AuthInterceptor’ class as part of our main app module providers after you have imported ‘HTTP_INTERCEPTORS’.
    app.module.ts

    import {NgModule} from '@angular/core';
    import {AuthInterceptor} from './auth-interceptor'
    import {HTTP_INTERCEPTORS} from '@angular/common/http';
    
    @NgModule({
      providers: [{
        provide: HTTP_INTERCEPTORS,
        useClass: AuthInterceptor,
        multi: true,
      }],
    })
    export class AppModule {}
    
  • Simple Javascript function to convert to timeAgo.js

    Calculate the time difference for javascript date objects in years, months, days, hours, minutes and seconds. Whether they are in the future or in the past. The function accounts for all very easily. Since this is a lightweight function you can easily use this as part of any application, without incurring much overhead.

    Code

    var timeAgo = function(date) {
      var d = new Date();
      var UTCsecondsNow = (d.getTime() + d.getTimezoneOffset() * 60 * 1000);
      var UTCseconds = (date.getTime() + date.getTimezoneOffset() * 60 * 1000);
      var diff = UTCsecondsNow - UTCseconds;
      var tense = 'ago';
      if (diff < 0) {
        tense = 'later';
        diff = Math.abs(diff);
      }
      if (diff === 0) return 0;
      // 365.25 * 24 * 60 * 60 * 1000
      var years = singular(Math.round(diff / 31557600000), 'Year');
      if (years)
        return years + tense;
      var months = singular(Math.round(diff / 2592000000), 'Month');
      if (months)
        return months + tense;
      var days = singular(Math.round(diff / 86400000), 'Day');
      if (days)
        return days + tense;
      var hours = singular(Math.round(diff / 3600000), 'Hour');
      if (hours)
        return hours + tense;
      var mins = singular(Math.round(diff / 60000), 'Minute');
      if (mins)
        return mins + tense;
      var secs = singular(Math.round(diff / 1000), 'Second');
      if (secs)
        return secs + tense;
    };
    
    var singular = function(num, str) {
      if (num > 1) {
        if (num === 1)
          return '1 ' + str + ' ';
        else
          return num + ' ' + str + 's ';
      }
      return '';
    };
    

    Usage

    timeAgo( new Date('2016-12-04T11:45:00.000Z') )

    Output

    10 Months ago

  • Refresh your app automatically in the browser with gulp & livereload

    Add livereload to your dev in 5 mins

    You will need to install gulp-server-livereload for this. This utilizes web sockets. Make sure you have a compatible version of node+npm before you run this. This will install gulp-server-livereload as a dev dependency in your node modules folder and add it to your package.json file.

    npm i gulp-server-livereload --save -D

    Add the following code to gulpfile.js and run gulp livereload, it should open up your default browser and load your app at localhost:8000.
    Note: Make sure you have an index.html file in your app inside the public folder.

    var gulp = require('gulp');
    var server = require('gulp-server-livereload');
    gulp.task('livereload', function() {
      gulp.src('public')
        .pipe(server({
          livereload: true,
          directoryListing: false,
          open: true
        }));
    });
    
  • Invalid Object & Array Manipulations in Vue.js 2

    Objects

      let obj = {name: 'Shiva'
                 occupation: 'coder'}
    delete obj.name
    // or delete obj['name']
    obj.name = 'Charan'
    // or obj['name'] = 'Charan'
    

    This is how you would usually set delete/add/set properties in Javascript. But Vue.js 2 can’t detect the changes if the object is manipulated in this fashion.
    For it to be able to detect these changes, use the following.

    Vue.set(obj, 'name', 'Shiva')
    

    or

    this.$set(obj, 'name', 'Shiva')
    

    Arrays

    Similarly for arrays, if we use the following, then Vue.js 2 fails to detect the changes in state.

    let arr = [1,2,3,4]
    arr[0] = 9
    

    You will have to use the following commands to be able to deal with the above situation and many others.
    Vue.js 2 has wrapped methods to help us create work arounds for such issues.

    // Vue.set
    this.$set(arr, 0, 9)
    // or
    arr.splice(0, 1, 9)

    Wrapped methods

    • push()
    • pop()
    • shift()
    • unshift()
    • splice()
    • sort()
    • reverse()