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5 object methods you must know as a javascript Developer

siradji profile image Siradji Awoual Updated on ・2 min read

Almost everything is an object in javascript and unfortunately, not all of us know the goodies that it comes with.

In this article, i will show you the five most used Object methods and their examples.

1. Object.assign()

This is perhaps the most used object method in javascript. So basically, this method copies all the values from one or more source to a targeted object.

const chevrolet = {
  type: 'sedan',
  price: 10000,
  isLuxury: true,
};
const honda = Object.assign(chevrolet);

console.log(honda);
// {type: "sedan", price: 10000, isLuxury: true}
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In the above code block, we created a new object chevrolet that hold some data in it.
And for some reason we want another object with the same data. So we basically copy the data inside of chevrolet to honda using the assign method.

2. Object.create()

This method is quite similar to Object.assign() — you can make a new object base on a reference object. However, the difference is that objects created with the assign() method are linked with the reference object. Changes made to one of them will affect the other (inheritance chain).

//  with  assign
const chevrolet = {
  type: 'sedan',
  price: 10000,
  isLuxury: true,
};
const honda = Object.assign(chevrolet);

honda.price = 2000; // this will overwrite both
//  the price property in honda
//  and chevrolet

console.log(chevrolet);
// {type: "sedan", price: 2000, isLuxury: true}

//  with object.create
const chevrolet = {
  type: 'sedan',
  price: 10000,
  isLuxury: true,
};
const honda = Object.create(chevrolet);

honda.price = 2000;
//  change will not affect reference object (chevrolet)

console.log(chevrolet);
// {type: "sedan", price: 10000, isLuxury: true}

console.log(honda);
// {type: "sedan", price: 2000, isLuxury: true}
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3. Object.entries()

The entries.() method return an array with all the data (key/values) inside of an object.

const chevrolet = {
  type: 'sedan',
  price: 10000,
  isLuxury: true,
};

const chevArr = Object.entries(chevrolet);

console.log(chevArr);
// [ [type,sedan,], [price,10000,], [isLuxury,true,]]
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4. Object.freeze()

This method literally freeze an object making it immutable. Properties can not be changed or deleted.

const chevrolet = {
  type: 'sedan',
  price: 10000,
  isLuxury: true,
};
Object.freeze(chevrolet);

chevrolet.price = 20000;

console.log(chevrolet.price);
//  10000 instead of 20000.
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5. Object. is()

This method compares two objects and return a boolean.

const chevrolet = {
  type: 'sedan',
  price: 10000,
  isLuxury: true,
};
const honda = Object.assign(chevrolet);

const isEqual = Object.is(honda, chevrolet);

console.log(isEqual);
//  true
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Update: if you like this, you should checkout my article on array methods
That is it guys and i hope you learn something from this.
Happy coding.

Discussion (7)

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devworkssimone profile image
DevWorksSimone

I would emphasize that Object.freeze() freeze just 1st level not the nested properties

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siradji profile image
Siradji Awoual Author • Edited

Totally forgot about that. I'd add that. Thanks for pointing out.

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Gizem Ulubayam

Nice post. I hope you continue the posts like this javaScript posts.

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siradji profile image
Siradji Awoual Author

I am glad you like it. I will be writing about arrays and their method soon. Thanks

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fblind profile image
Facundo Soria

Hey, nice post!.
It made me realize that I should use Object.create a lot more. In general I use Object.assign with an empty object to create a new object (something like Object.assign({}, chevrolet))

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siradji profile image
Siradji Awoual Author

I am glad you liked it.

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kahn profile image
Karim Hussain • Edited

One of my most often used methods is the Object.prototype.hasOwnProperty() to check if the object has a specific property.

This allows you to avoid reference exceptions.

Note: Make sure you use this by calling the method from the Object prototype like this: Object.hasOwnProperty.call(obj, "property")

Why you might ask? It is because if the object you are trying to call this method from is null you will run into an exception. By making use of call you can avoid this from happening.

A very rare scenario would also be that if you call hasOwnProperty from the object itself, the method could have been mutated.

Enjoy :)