how to use property of object in loop?

Question

I want to have a loop with some properties of a class, not all of it's properties. I want to implement a function for properties of the class. But even I don't know how to set the length of loop with number of properties in class. For example this is my class:

class Address{
id: number,
street: string,
state: string,
}

and I want to make a loop with length of the object of this class and do something on each property of this object of Address class, something like this:

for (let i; i< /*length of address object*/; i++) {
if (/*each property of address */) {
// do sth
 }
}

I'm using Angular 4. Thank you

Sajeetharan · Accepted Answer · 2018-01-11 17:58:32Z

1

LOOP OVER ARRAY OF OBJECTS:

I assume you are refering to array of objects, with that you can do

for(let result of this.address){
    console.log(result.street);
    ....
    etc
}

LOOP OVER OBJECT KEYS :

in case if its an object, you can get the keys using Object.keys and then loop over them.

objectKeys = Object.keys(this.address);

for (let result of this.objectKeys) {
    console.log('key', result);
    console.log('value', this.address[result]);
}

edited Jan 11, 2018 at 17:58

answered Jan 11, 2018 at 16:08

Sajeetharan

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3 Comments

Lazar Ljubenović Over a year ago

An array of objects can be looped just like OP did in the question, which means the question is not about taht.

Amir Gh Over a year ago

thanks a lot @Sajeetharan. it works. but could you please describe what this.address[ ] do? I mean what is the brackets here?

Sajeetharan Over a year ago

it means you are accessing the value using the key of object. you can use myobject['name'] or myobject.name

Sachila Ranawaka · Accepted Answer · 2018-01-11 16:09:42Z

1

Create a new instance of address class and get the object properties using Object.keys

address: Address = new Address()

keyArr = Object.keys(this.address)

for (let i; i< this.keyArr ; i++) {
if (/*each property of address */) {
// do sth
 }
}

answered Jan 11, 2018 at 16:09

Sachila Ranawaka

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2 Comments

Amir Gh Over a year ago

thank you @Sachila Ranawaka it is close to what I want, but the keyArr is the name of properties of that address obj, for example: id-street-state. how can I get the value of these properties?

Amir Gh Over a year ago

no when I log keyArr it's an array with 3 properties ['id','street','state'], what is your idea to get the value of these properties?

Lazar Ljubenović · Accepted Answer · 2018-01-11 16:09:06Z

0

Since you've tagged this as an Angular question, I'll assume you want to print this in Angular template. Otherwise it's not Angular at all.

You cannot loop over objects because there is no specified order in which the loop should happen. You must convert your object into an array. One way to do this is to use Object.keys method.

this.keys = Object.keys(object)

Then loop over this in your template:

<ul>
  <li *ngFor="let key of keys">{{ key }} {{ object[key] }}</li>
</ul>

answered Jan 11, 2018 at 16:09

Lazar Ljubenović

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Comments

Santosh · Accepted Answer · 2018-01-11 17:20:08Z

0

I assume that you want to access property of each Address Object. assuming that : addresses: Address[];

You need to use underscore.js library first and import it in your class.

import * as _ from 'underscore'

Now you can use '_' function in your code as follow:

do(addresses=> {
    _.each(addresses, (address: Address) => {
          if (address.state === "CA") {
            console.log('This is California.');
          }
     });
  });

answered Jan 11, 2018 at 17:20

Santosh

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