JS merge two objects doesnt works

Question

I try to use the following to merge object which doesn't works, what I need that if this.options have the property put it on this.props otherwise use the this.props defaults.

Any idea how I can merge it in a shorter way, I've more fields that are doing the same

this.props!.hostName = this.options.hostName || this.props!.hostName;
this.props!.eventType = this.options.eventType || this.props!.eventType;
this.props!.eventTypeVersion = this.options.eventTypeVersion || this.props!.eventTypeVersion;
this.props!.uri = this.options.uri || this.props!.uri;

i've tried the following which doesnt works

this.props = Object.assign(this.props, this.options);

and also this

this.props = Object.assign(this.options, this.props);

https://stackoverflow.com/questions/13852852/how-do-i-merge-two-javascript-objects-together-in-es6 — epascarello, Sep 17 '20 at 13:19

V.Tur · Answer 1 · 2020-09-17T14:02:12.057

1

Use spread operator:

{...props, ...options}

OR

for (const [k, v] of Object.entries(props)) {
  props[k] = options[k] || v
};

edited Sep 17 '20 at 14:02

answered Sep 17 '20 at 13:19

V.Tur

1,115
9
20

That's exactly the same as using the Object.assign() – Tasos Sep 17 '20 at 13:20

score 1 · Accepted Answer · answered Sep 17 '20 at 13:38

Your first attempt, Object.assign(this.props, this.options) should work. If it doesn't that probably means that this.options has some falsy properties which you want to ignore. You can try filtering those out:

const truthyOptions = Object.entries(this.options)
    .filter(([k,v]) => v)
    .map(([k, v]) => ({[k]: v}))

this.props = Object.assign(this.props, ...truthyOptions)

JS merge two objects doesnt works

2 Answers2