Iterating over a dictionary in Javascript

Question

I am fairly new to Javascript- and trying to iterate over a dictionary in Javascript. I can easily do so in python:

for key, value in dict.items():
    //do something

Is there a similar way to do the same in Javascript?

Structure I am trying to iterate over is:

{ 'meta.num_prod': 4,
  'meta.crtd_on': '2015-12-24T06:27:18.850Z',
  'meta.last_upd': '2015-12-24T06:46:12.888Z',
  's.103114': 
     { prod_id: '103114',
       product_type: 'normal',
       last_updated: '2015-12-24T06:28:44.281Z',
       qty: 3,
       created_on: '2015-12-24T06:27:18.850Z' },
  's.103553': 
     { prod_id: '103553',
       product_type: 'normal',
       last_updated: '2015-12-24T06:46:12.888Z',
       qty: 1,
       created_on: '2015-12-24T06:46:12.888Z' } }

Answer 1

There are multiple ways to this one standard way is using Object.keys:

You can do

• Object.keys
• Array.Prototype.forEach

Object.keys(obj).forEach(function(key) {
   console.log(key + " " + obj[key]);
});

If you are using jQuery you can use $.each() method like this:

$.each({ name: "John", lang: "JS" }, function( k, v ) {
  console.log( "Key: " + k + ", Value: " + v );
});

Or you can use a for...in loop, but most people I know don't use them nowadays due to better alternatives.

for (var prop in obj) {
  console.log("obj." + prop + " = " + obj[prop]);
}

If you ever end up wanting to complicate things you can use es6 generators like this to get syntax more akin to python:

// The asterisk after `function` means that
// `objectEntries` is a generator
function* objectEntries(obj) {
    let propKeys = Reflect.ownKeys(obj);

    for (let propKey of propKeys) {
        // `yield` returns a value and then pauses
        // the generator. Later, execution continues
        // where it was previously paused.
        yield [propKey, obj[propKey]];
    }
}

let jane = { first: 'Jane', last: 'Doe' };
for (let [key,value] of objectEntries(jane)) {
    console.log(`${key}: ${value}`);
}
// Output:
// first: Jane
// last: Doe

Answer 2

EcmaScript 2017 has Object.entries that comes in handy in situations like this one. MDN

const obj = { 
    'meta.num_prod': 4,
    'meta.crtd_on': '2015-12-24T06:27:18.850Z',
    'meta.last_upd': '2015-12-24T06:46:12.888Z',
}

Object.entries(obj).forEach(function([key, value]) {
   console.log(`${key} ${value}`);
});

Output:

meta.num_prod 4
meta.crtd_on 2015-12-24T06:27:18.850Z
meta.last_upd 2015-12-24T06:46:12.888Z