CODEWITHSUNDEEP
javascriptnode.jsunderscore.jslodash
Rock
Rock

Reputation: 758

How to make object values as `null` or `undefined` if the property not found in the Object using Lodash

Hi I am having an object like this, I want to return the property values as undefined or null if not present in the object. Here is my object.

var build= { 'ts1': 1, 'ts2': '2', 'ts3': 3 };

I am using _.pick function to pick the values it only pick values that are present in the object. Here is my code:

_.pick(build, [ 'ts0' 'ts1', 'ts2','ts5','ts6','ts7']);

I am getting the result like this:

 { 'ts1': 1, 'ts2': '2'}

and the expected output is:

{ 'ts0':null, 'ts1': 1, 'ts2': '2','ts5':null,'ts6':null,'ts7':null}

Please can anybody help me on this.

Upvotes: 0

Views: 2199

Answers (4)

Mike
Mike

Reputation: 1634

You can iterate through the desired values and build a new object. _.set will add the value to the new object. _.get will attempt to get the value from the existing object, if it does not exist then it will use null as the default value.

var build = {
  'ts1': 1,
  'ts2': '2',
  'ts3': 3
};
var pickValues = ['ts0', 'ts1', 'ts2', 'ts5', 'ts6', 'ts7'];
var result = {};
_.forEach(pickValues, function(key) {
  _.set(result, key, _.get(build, key, null));
});
console.log(result);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

Upvotes: 1

gyre
gyre

Reputation: 16779

_.pick is designed to give you a subset of the properties of an object. It will not assign a property to null that had never existed in the original object.

However, you mentioned that:

I want to return the property values as undefined or null if not present in the object

Luckily for you, JavaScript already does this by default (returning undefined) for all property accesses where the property does not exist on the target object. So, you could simply use the code you have already and use regular bracket property access notation to have property values default to undefined:

var build = {
  'ts1': 1,
  'ts2': '2',
  'ts3': 3
}

var result = _.pick(build, [
  'ts0', 'ts1', 'ts2', 'ts5', 'ts6', 'ts7'
])

console.log(result['ts0']) //=> undefined
console.log(result['ts1']) //=> 1
<script src="//cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

Edit: If you really need the properties to exist on the object and default to null, you can use the following method:

var build = {
  'ts1': 1,
  'ts2': '2',
  'ts3': 3
}

var result = _.reduce([
  'ts0', 'ts1', 'ts2', 'ts5', 'ts6', 'ts7'
], function (o, e) {
  o[e] = e in build ? build[e] : null
  return o
}, {})

console.log(result['ts0']) //=> undefined
console.log(result['ts1']) //=> 1
<script src="//cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

Upvotes: 4

guest271314
guest271314

Reputation: 1

You can use for..of loop to iterate array, assign properties to object, set value to value of build at that property, or null

var build = { 'ts1': 1, 'ts2': '2', 'ts3': 3 };
let props = ['ts0', 'ts1', 'ts2','ts5','ts6','ts7'];
let res = {};
for (let prop of props) res[prop] = build[prop] || null;
console.log(res);

Upvotes: 1

Jordan Soltman
Jordan Soltman

Reputation: 3883

That's just not how _.pick works. You could use _.assign to accomplish what you are trying to do.

var build = {
  'ts1': 1,
  'ts2': '2',
  'ts3': 3
};

let result = _.assign({
  ts0: null,
  ts1: null,
  ts2: null,
  ts3: null,
  ts4: null,
  ts5: null,
  ts6: null,
  ts7: null
},
build);

console.log(result);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

Upvotes: 0

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