set attribute on objects by attribute string Javascript

Question

I have Knockout For Students book, and looking at AJAX:

    self.loadUserData = function(){
        $.getJSON("http://127.0.0.1:5000/data", function(data){
            self.firstName(data.firstName);
            self.lastName(data.lastName);
            self.activities(data.activities);
            self.favoriteHobby(data.favoriteHobby);
        });
    }
}

The full code looks like

ajax-chapter-7.html:

<html lang='en'>
<head>
  <title>External data</title>
  <meta charset='utf-8' />
  <link rel='stylesheet' href='style.css' />
</head>
<body>
  <h1>External data</h1>

  <form action="#" method="post">
      <p>
          First name: <input data-bind='value: firstName' />
      </p>
      <p>
          Last name: <input data-bind='value: lastName' />
      </p>
      <div>
          Your favorite hobby:
          <select data-bind='options: activities, value: favoriteHobby'></select>
      </div>
      <p>
          <button data-bind='click: loadUserData'>Load Data</button>
      </p>
  </form>

  <script type='text/javascript' src='knockout-3.4.0.js'></script>
  <script type='text/javascript' src='jquery-3.1.1.min.js'></script>
  <script type='text/javascript'>
    function PersonViewModel(){
        var self = this;
        self.firstName = ko.observable("");
        self.lastName = ko.observable("Johnson");
        self.activities = ko.observableArray([]);
        self.favoriteHobby = ko.observable("");

        // http://stackoverflow.com/questions/25011952/can-you-add-headers-to-getjson-in-jquery

        $.ajaxSetup({
            headers: {
                // 'Origin': 'http://example.com'
            }
        })

        self.loadUserData = function(){
            $.getJSON("http://127.0.0.1:5000/data", function(data){
                Object.keys(data).forEach(function(k){
                    alert(k);
                    alert(data[k]);
                    alert(self[k]);
                    self[k] = data[k];
                });
                // self.firstName(data.firstName);
                // self.lastName(data.lastName);
                // self.activities(data.activities);
                // self.favoriteHobby(data.favoriteHobby);
            });
        }
    }

    ko.applyBindings(new PersonViewModel());
  </script>
</body>
</html>

server.py:

from flask import Flask, jsonify
from flask_cors import CORS, cross_origin

app = Flask(__name__)
CORS(app)


@app.route('/')
def hello():
    return 'Hello, world'


# http://stackoverflow.com/questions/13081532/how-to-return-json-using-flask-web-framework
@app.route('/data')
def data():
    data = {
        'firstName': 'Cody',
        'lastName': 'Childers',
        'activities': [
            'Golf',
            'Kayaking',
            'Web development',
        ],
        'favoriteHobby': 'Golf',
    }

    return jsonify(**data)


if __name__ == "__main__":
    app.run()

The book and code is all working, but the loadUserData is hideous and repetitive. In python we can do this like:

keys = ['firstName', 'lastName', 'activities', 'favoriteHobby']
for key in keys:
    setattr(self, key, getattr(data, key))

boom, done.

Is there a Javascript equivalent to set attributes on self by string, assuming I knew the JSON keys I get are the same as attribute names I wanna set?

Knockout will require me to call attributes as a function, not set them as normal attributes (knockout calls it 'observables').

Thank you

baao · Accepted Answer · 2016-11-04 22:07:33Z

4

You can use bracket notation and Object.keys()

$.getJSON("http://127.0.0.1:5000/data", function(data){
    Object.keys(data).forEach(function(k) {
        // you may check if the key is in the "to be transferred ones" here
        self[k] = data[k]; 
    });
});

If you want to assign only certain keys, you can use

var allowedKeys = ['firstName', 'lastName', 'activities', 'favoriteHobby']
$.getJSON("http://127.0.0.1:5000/data", function(data){
    Object.keys(data).forEach(function(k) {
        if (allowedKeys.indexOf(k) > -1) self[k] = data[k]; 
    });
});

Alternatively, you can also use Object.assign(), but without the possibility to exclude some keys:

$.getJSON("http://127.0.0.1:5000/data", function(data){
    self = Object.assign(self, data);
});

And for your comment, if you need to call a function (though you should add a check if the function exists before executing it):

$.getJSON("http://127.0.0.1:5000/data", function(data){
    Object.keys(data).forEach(function(k) {
        // you may check if the key is in the "to be transferred ones" here
        self[k](data[k]); 
    });
});

edited Nov 4, 2016 at 22:07

answered Nov 4, 2016 at 21:56

baao

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3 Comments

codyc4321 Over a year ago

this can't work, as observables in knockoutjs are functions. I'm looking at it now

baao Over a year ago

Edited a version with function calls @codyc4321

baao Over a year ago

gerne @codyc4321 :-)

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