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javascript numbers- immutable
I read Douglas Crockford's book JavaScript: the Good Parts. It says the number in JavaScript is immutable. But numbers in JavaScript is copied by value and we can use operator ++ to change the value. So why say it's immutable? and further, if it's immutable, why numbers are copied by value?
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In JavaScript String and Numbers are immutable data types. JavaScript is not a good language to work with data in an immutable fashion. In JavaScript Arrays and Objects are not immutable. Their values can be changed over time.
String specifications among programming languages vary, however most languages treat them as reference types. But strings in JavaScript are different. They are immutable primitives. This means that the characters within them may not be changed and that any operations on strings actually create new strings.
Arrays and Objects Are Mutable Arrays and objects are not immutable in JavaScript because they can indeed change their value over time.
They are immutable because they are copied by value.
When you do
var x = 4;
x += 1;
you haven't changed the number 4 into the number 5. You have changed the value stored in the variable x from 4 to 5.
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