[angular] Iterate over object in Angular

I am trying to do some things in Angular 2 Alpha 28, and am having an issue with dictionaries and ngFor.

I have an interface in TypeScript looking like this:

interface Dictionary {
    [index: string]: string
}

In JavaScript this will translate to an object that with data might look like this:

myDict={'key1':'value1','key2':'value2'}

I want to iterate over this and tried this:

<div *ngFor="(#key, #value) of myDict">{{key}}:{{value}}</div>

But to no avail, none of the below worked either:

<div *ngFor="#value of myDict">{{value}}</div>
<div *ngFor="#value of myDict #key=index">{{key}}:{{value}}</div>

In all cases I get errors like Unexpected token or Cannot find 'iterableDiff' pipe supporting object

What am I missing here? Is this not possible anymore? (The first syntax works in Angular 1.x) or is the syntax different for iterating over an object?

The dictionary is an object, not an array. I believe ng-repeat requires an array in Angular 2.

The simplest solution would be to create a pipe/filter that converts the object to an array on the fly. That said, you probably want to use an array as @basarat says.

//Get solution for ng-repeat    
//Add variable and assign with Object.key

    export class TestComponent implements OnInit{
      objectKeys = Object.keys;
      obj: object = {
        "test": "value"
        "test1": "value1"
        }
    }
    //HTML
      <div *ngFor="let key of objectKeys(obj)">
        <div>
          <div class="content">{{key}}</div>
          <div class="content">{{obj[key]}}</div>
        </div>

Angular 6.1.0+ Answer

Use the built-in keyvalue-pipe like this:

<div *ngFor="let item of myObject | keyvalue">
    Key: <b>{{item.key}}</b> and Value: <b>{{item.value}}</b>
</div>

or like this:

<div *ngFor="let item of myObject | keyvalue:mySortingFunction">
    Key: <b>{{item.key}}</b> and Value: <b>{{item.value}}</b>
</div>

where mySortingFunction is in your .ts file, for example:

mySortingFunction = (a, b) => {
  return a.key > b.key ? -1 : 1;
}

Stackblitz: https://stackblitz.com/edit/angular-iterate-key-value

You won't need to register this in any module, since Angular pipes work out of the box in any template.

It also works for Javascript-Maps.

In JavaScript this will translate to an object that with data might look like this

Interfaces in TypeScript are a dev time construct (purely for tooling ... 0 runtime impact). You should write the same TypeScript as your JavaScript.

I have been tearing my hair out with trying to parse and use data returned form a JSON query/ api call. Im not sure exactly where i was going wrong, i feel like i have been circling the answer for days, chasing various error codes like:

"Cannot find 'iterableDiff' pipe supporting object"

"Generic TYpe Array requires one argument(s)"

JSON parsing Errors, and im sure others

Im assuming i just had the wrong combination of fixes.

So here's a bit of a summary of gotchas and things to look for.

Firstly check the result of your api calls, your results may be in the form of an object, an array, or an array of objects.

i wont go into it too much, suffice to say the OP's original Error of not being iterable is generally caused by you trying to iterate an object, not an Array.

Heres some of my debugging results showing variables of both arrays and objects

So as we generally would like to iterate over our JSON result we need to ensure it is in the form of an Array. I tried numerous examples, and perhaps knowing what i know now some of those would in fact work, but the approach i went with was indeed to implement a pipe and the code i used was that the posted by t.888

   transform(obj: {[key: string]: any}, arg: string) {
if (!obj)
        return undefined;

return arg === 'keyval' ?
    Object.keys(obj).map((key) => ({ 'key': key, 'value': obj[key] })) :
  arg === 'key' ?
    Object.keys(obj) :
  arg === 'value' ?
    Object.keys(obj).map(key => obj[key]) :
  null;

Honestly i think one of the things that was getting me was the lack of error handling, by adding the 'return undefined' call i believe we are now allowing for non expected data to be sent to the pipe, which obviously was occurring in my case.

if you don't want to deal with argument to the pipe (and look i don't think it's necessary in most cases) you can just return the following

       if (!obj)
          return undefined;
       return Object.keys(obj);

Some Notes on creating your pipe and page or component that uses that pipe

is i was receiving errors about ‘name_of_my_pipe’ not being found

Use the ‘ionic generate pipe’ command from the CLI to ensure the pipe modules.ts are created and referenced correctly. ensure you add the following to the mypage.module.ts page.

import { PipesModule } from ‘…/…/pipes/pipes.module’;

(not sure if this changes if you also have your own custom_module, you may also need to add it to the custommodule.module.ts)

if you used the 'ionic generate page' command to make your page, but decide to use that page as your main page, remember to remove the page reference from app.module.ts (here's another answer i posted dealing with that https://forum.ionicframework.com/t/solved-pipe-not-found-in-custom-component/95179/13?u=dreaser

In my searching for answers there where a number of ways to display the data in the html file, and i don't understand enough to explain the differences. You may find it better to use one over another in certain scenarios.

            <ion-item *ngFor="let myPost of posts">
                  <img src="https://somwhereOnTheInternet/{{myPost.ImageUrl}}"/>
                  <img src="https://somwhereOnTheInternet/{{posts[myPost].ImageUrl}}"/>
                  <img [src]="'https://somwhereOnTheInternet/' + myPost.ImageUrl" />
            </ion-item>

However what worked that allowed me to display both the value and the key was the following:

    <ion-list>  
      <ion-item *ngFor="let myPost of posts  | name_of_pip:'optional_Str_Varible'">

        <h2>Key Value = {{posts[myPost]}} 

        <h2>Key Name = {{myPost}} </h2>

      </ion-item>
   </ion-list>  

to make the API call it looks like you need to import HttpModule into app.module.ts

import { HttpModule } from '@angular/http';
 .
 .  
 imports: [
BrowserModule,
HttpModule,

and you need Http in the page you make the call from

import {Http} from '@angular/http';

When making the API call you seem to be able to get to the children data (the objects or arrays within the array) 2 different ways, either seem to work

either during the call

this.http.get('https://SomeWebsiteWithAPI').map(res => res.json().anyChildren.OrSubChildren).subscribe(
        myData => {

or when you assign the data to your local variable

posts: Array<String>;    
this.posts = myData['anyChildren'];

(not sure if that variable needs to be an Array String, but thats what i have it at now. It may work as a more generic variable)

And final note, it was not necessary to use the inbuilt JSON library however you may find these 2 calls handy for converting from an object to a string and vica versa

        var stringifiedData = JSON.stringify(this.movies);                  
        console.log("**mResults in Stringify");
        console.log(stringifiedData);

        var mResults = JSON.parse(<string>stringifiedData);
        console.log("**mResults in a JSON");
        console.log(mResults);

I hope this compilation of info helps someone out.

If someone is wondering how to work with multidimensional object, here is the solution.

lets assume we have following object in service

getChallenges() {
    var objects = {};
    objects['0'] = { 
        title: 'Angular2', 
        description : "Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur."
    };

    objects['1'] = { 
        title: 'AngularJS', 
        description : "Lorem Ipsum is simply dummy text of the printing and typesetting industry."
    };

    objects['2'] = { 
        title: 'Bootstrap',
        description : "Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.",
    };
    return objects;
}

in component add following function

challenges;

constructor(testService : TestService){
    this.challenges = testService.getChallenges();
}
keys() : Array<string> {
    return Object.keys(this.challenges);
}

finally in view do following

<div *ngFor="#key of keys();">
    <h4 class="heading">{{challenges[key].title}}</h4>
    <p class="description">{{challenges[key].description}}</p>
</div>

Angular 2.x && Angular 4.x do not support this out of the box

You can use this two pipes to iterate either by key or by value.

Keys pipe:

import {Pipe, PipeTransform} from '@angular/core'

@Pipe({
  name: 'keys',
  pure: false
})
export class KeysPipe implements PipeTransform {
  transform(value: any, args: any[] = null): any {
    return Object.keys(value)
  }
}

Values pipe:

import {Pipe, PipeTransform} from '@angular/core'

@Pipe({
  name: 'values',
  pure: false
})
export class ValuesPipe implements PipeTransform {
  transform(value: any, args: any[] = null): any {
    return Object.keys(value).map(key => value[key])
  }
}

How to use:

let data = {key1: 'value1', key2: 'value2'}

<div *ngFor="let key of data | keys"></div>
<div *ngFor="let value of data | values"></div>

So I was going to implement my own helper function, objLength(obj), which returns just Object(obj).keys.length. But then when I was adding it to my template *ngIf function, my IDE suggested objectKeys(). I tried it, and it worked. Following it to its declaration, it appears to be offered by lib.es5.d.ts, so there you go!

Here's how I implemented it (I have a custom object that uses server-side generated keys as an index for files I've uploaded):

        <div *ngIf="fileList !== undefined && objectKeys(fileList).length > 0">
          <h6>Attached Files</h6>
          <table cellpadding="0" cellspacing="0">
            <tr *ngFor="let file of fileList | keyvalue">
              <td><a href="#">{{file.value['fileName']}}</a></td>
              <td class="actions">
                <a title="Delete File" (click)="deleteAFile(file.key);">
                </a>
              </td>
            </tr>
          </table>
        </div>

Updated : Angular is now providing the pipe for lopping through the json Object via keyvalue :

<div *ngFor="let item of myDict | keyvalue">
  {{item.key}}:{{item.value}}
</div>

WORKING DEMO , and for more detail Read

Previously (For Older Version) : Till now the best / shortest answer I found is ( Without any Pipe Filter or Custom function from Component Side )

Component side :

objectKeys = Object.keys;

Template side :

<div *ngFor='let key of objectKeys(jsonObj)'>
   Key: {{key}}

    <div *ngFor='let obj of jsonObj[key]'>
        {{ obj.title }}
        {{ obj.desc }}
    </div>

</div>

WORKING DEMO

try to use this pipe

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({ name: 'values',  pure: false })
export class ValuesPipe implements PipeTransform {
  transform(value: any, args: any[] = null): any {
    return Object.keys(value).map(key => value[key]);
  }
}

<div *ngFor="#value of object | values"> </div>

Define the MapValuesPipe and implement PipeTransform:

import {Pipe, PipeTransform} from '@angular/core';

@Pipe({name: 'mapValuesPipe'})
export class MapValuesPipe implements PipeTransform {
    transform(value: any, args?: any[]): Object[] {
        let mArray: 
        value.forEach((key, val) => {
            mArray.push({
                mKey: key,
                mValue: val
            });
        });

        return mArray;
    }
}

Add your pipe in your pipes module. This is important if you need to use the same pipe in more than one components:

@NgModule({
  imports: [
    CommonModule
  ],
  exports: [
    ...
    MapValuesPipe
  ],
  declarations: [..., MapValuesPipe, ...]
})
export class PipesAggrModule {}

Then simply use the pipe in your html with *ngFor:

<tr *ngFor="let attribute of mMap | mapValuesPipe">

Remember, you will need to declare your PipesModule in the component where you want to use the pipe:

@NgModule({
  imports: [
    CommonModule,
    PipesAggrModule
  ],
...
}
export class MyModule {}

Adding to SimonHawesome's excellent answer. I've made an succinct version which utilizes some of the new typescript features. I realize that SimonHawesome's version is intentionally verbose as to explain the underlying details. I've also added an early-out check so that the pipe works for falsy values. E.g., if the map is null.

Note that using a iterator transform (as done here) can be more efficient since we do not need to allocate memory for a temporary array (as done in some of the other answers).

import {Pipe, PipeTransform} from '@angular/core';

@Pipe({
    name: 'mapToIterable'
})
export class MapToIterable implements PipeTransform {
    transform(map: { [key: string]: any }, ...parameters: any[]) {
        if (!map)
            return undefined;
        return Object.keys(map)
            .map((key) => ({ 'key': key, 'value': map[key] }));
    }
}

There's another way to loop over objects, using structural directives:

I prefer this approach because it "feels" most like the normal ngFor loop. :-)

(In this case for example I added Angular's context variables let i = index | even | odd | first | last | count) that are accessible inside my loop).

@Directive({
  selector: '[ngForObj]'
})
export class NgForObjDirective implements OnChanges {

  @Input() ngForObjOf: { [key: string]: any };

  constructor(private templateRef: TemplateRef<any>, private viewContainerRef: ViewContainerRef) { }

  ngOnChanges(changes: SimpleChanges): void {
    if (changes.ngForObjOf && changes.ngForObjOf.currentValue) {
      // remove all views
      this.viewContainerRef.clear();

      // create a new view for each property
      const propertyNames = Object.keys(changes.ngForObjOf.currentValue);
      const count = propertyNames.length;

      propertyNames.forEach((key: string, index: number) => {
        const even = ((index % 2) === 0);
        const odd = !even;
        const first = (index === 0);
        const last = index === (count - 1);

        this.viewContainerRef.createEmbeddedView(this.templateRef, {
          $implicit: changes.ngForObjOf.currentValue[key],
          index,
          even,
          odd,
          count,
          first,
          last
        });
      });
    }
  }
}

Usage in your template:

<ng-container *ngForObj="let item of myObject; let i = index"> ... </ng-container>

And if you want to loop using an integer value, you can use this directive:

@Directive({
   selector: '[ngForInt]'
})
export class NgForToDirective implements OnChanges {

  @Input() ngForIntTo: number;
 
  constructor(private templateRef: TemplateRef<any>, private viewContainerRef: ViewContainerRef) {

  }

  ngOnChanges(changes: SimpleChanges): void {
    if (changes.ngForIntTo && changes.ngForIntTo.currentValue) {
      // remove all views
      this.viewContainerRef.clear();

      let currentValue = parseInt(changes.ngForIntTo.currentValue);
      for (let index = 0; index < currentValue; index++) {
        this.viewContainerRef.createEmbeddedView(this.templateRef, {
          $implicit: index,
          index
        });
      }

    }

  }
}

Usage in your template (example: loop from 0 to 14 (= 15 iterations):

<ng-container *ngForInt="let x to 15"> ... </ng-container>

In addition to @obscur's answer, here is an example of how you can access both the key and value from the @View.

Pipe:

@Pipe({
   name: 'keyValueFilter'
})

export class keyValueFilterPipe {
    transform(value: any, args: any[] = null): any {

        return Object.keys(value).map(function(key) {
            let pair = {};
            let k = 'key';
            let v = 'value'


            pair[k] = key;
            pair[v] = value[key];

            return pair;
        });
    }

}

View:

<li *ngFor="let u of myObject | 
keyValueFilter">First Name: {{u.key}} <br> Last Name: {{u.value}}</li>

So if the object were to look like:

myObject = {
    Daario: Naharis,
    Victarion: Greyjoy,
    Quentyn: Ball
}

The generated outcome would be:

First name: Daario
Last Name: Naharis

First name: Victarion
Last Name: Greyjoy

First name: Quentyn
Last Name: Ball

Here's a variation on some of the above answers that supports multiple transforms (keyval, key, value):

import { Pipe, PipeTransform } from '@angular/core';

type Args = 'keyval'|'key'|'value';

@Pipe({
  name: 'mapToIterable',
  pure: false
})
export class MapToIterablePipe implements PipeTransform {
  transform(obj: {}, arg: Args = 'keyval') {
    return arg === 'keyval' ?
        Object.keys(obj).map(key => ({key: key, value: obj[key]})) :
      arg === 'key' ?
        Object.keys(obj) :
      arg === 'value' ?
        Object.keys(obj).map(key => obj[key]) :
      null;
  }
}

Usage

map = {
    'a': 'aee',
    'b': 'bee',
    'c': 'see'
}

<div *ngFor="let o of map | mapToIterable">{{o.key}}: {{o.value}}</div>
  <div>a: aee</div>
  <div>b: bee</div>
  <div>c: see</div>

<div *ngFor="let o of map | mapToIterable:'keyval'">{{o.key}}: {{o.value}}</div>
  <div>a: aee</div>
  <div>b: bee</div>
  <div>c: see</div>

<div *ngFor="let k of map | mapToIterable:'key'">{{k}}</div>
  <div>a</div>
  <div>b</div>
  <div>c</div>

<div *ngFor="let v of map | mapToIterable:'value'">{{v}}</div>
  <div>aee</div>
  <div>bee</div>
  <div>see</div>

If you have es6-shim or your tsconfig.json target es6, you could use ES6 Map to make it.

var myDict = new Map();
myDict.set('key1','value1');
myDict.set('key2','value2');

<div *ngFor="let keyVal of myDict.entries()">
    key:{{keyVal[0]}}, val:{{keyVal[1]}}
</div>

I had a similar issue, built something for objects and Maps.

import { Pipe } from 'angular2/core.js';_x000D_
_x000D_
/**_x000D_
 * Map to Iteratble Pipe_x000D_
 * _x000D_
 * It accepts Objects and [Maps](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map)_x000D_
 * _x000D_
 * Example:_x000D_
 * _x000D_
 *  <div *ngFor="#keyValuePair of someObject | mapToIterable">_x000D_
 *    key {{keyValuePair.key}} and value {{keyValuePair.value}}_x000D_
 *  </div>_x000D_
 * _x000D_
 */_x000D_
@Pipe({ name: 'mapToIterable' })_x000D_
export class MapToIterable {_x000D_
  transform(value) {_x000D_
    let result = [];_x000D_
    _x000D_
    if(value.entries) {_x000D_
      for (var [key, value] of value.entries()) {_x000D_
        result.push({ key, value });_x000D_
      }_x000D_
    } else {_x000D_
      for(let key in value) {_x000D_
        result.push({ key, value: value[key] });_x000D_
      }_x000D_
    }_x000D_
_x000D_
    return result;_x000D_
  }_x000D_
}