[Javascript] Primitive value are immutable

标签：value   arw   color   imp   action   class   width   error   put   

There is a old bug in Javascript which is typeof(null) === ‘object‘, null is primitive value actually, but we have to live with this bug, fix it will break the world.

Primitive are immutable!

let reaction = ‘yikes‘;
reaction[0] = ‘l‘;
console.log(reaction);

What‘s the output of console log?

The Answer is:

yikes

In ‘strict mode‘; it will throw an error for that.

A String is a primitive value, and that means a great deal! All primitive values are immutable. Which means it is unchangeable, read-only. You can‘t mess with primitive values. AT ALL!

Variables are not values, Variable point to values

let pet = ‘Narwhal‘;
pet = ‘The Kraken‘;
console.log(pet);

What‘s the output again?

The Answer is:

// "The Kraken"

But what about Primitive value are immutable? 

Yes, but here, we assign to ‘pet‘ variable. We can change ‘pet‘ variable to "The Kraken".

[Javascript] Primitive value are immutable

标签：value   arw   color   imp   action   class   width   error   put   

原文地址：https://www.cnblogs.com/Answer1215/p/12327114.html