CODEWITHSUNDEEP
javascriptimmutability
Jamo
Jamo

Reputation: 504

What is the definition of immutability in Javascript? Is the same for every program language?

I know in JS the primitive values are immutable values and objects are mutable, but, what does it exactly mean?

For example: 

var foo = 1;

then we have

foo = 2;

did foo mutate?

Is that applicable for every language? or does everyone applies it under its own rules?

Upvotes: 0

Views: 46

Answers (2)

sheplu
sheplu

Reputation: 2975

As said by @Pointy, when you speak about immutability and mutability, you speak about values and not variables.

In JavaScript, strings and numbers are immutable by design. Maybe those example can help you understand https://www.sitepoint.com/immutability-javascript/

Upvotes: 2

marvel308
marvel308

Reputation: 10458

An Immutable Object is one whose state cannot be changed after it is created. It applies to values, If you want variables to be immutable they would have to be declared constant 

var str = 'hello world';

str[0] = '1';

// value remains unchanged
console.log(str);

const x = 1;
// err cannot change value
x = 2;
console.log(x);

Upvotes: 0

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