Overview of JavaScript ES6 features

Re:Overview of JavaScript ES6 features by josephg on Monday October 24, 2016 @09:37AM (#12778614)

The const keyword makes the object reference constant. It doesn't make the object's value constant. You can change the contents of 'info' (info.push(5) is fine). You just can't change which object the variable points to. (info = [] will throw).

If you know C/C++, the code 'const info = []' makes 'info' a constant pointer to a list not a pointer to a constant list.

If you want to stop a variable from being changed, use Object.freeze() - https://developer.mozilla.org/en/docs/Web/JavaScript/Referen...

[ Parent | on HN ]

Re:Overview of JavaScript ES6 features by samcodes on Monday October 24, 2016 @10:27AM (#12779054)

This was what I came to comment on; when introducing ES6 features, this always trips people up. Thanks for "constant pointer to a list, not pointer to a constant list", I will use that next time I explain this.

This also means that objects defined with const can be mutated:

const x = { y: 2 }; x.y = 3;

Doesn't error. However with types that are immutable, like numbers and strings, const really is a constant: const HELLO = "hi" will never change.

[ Parent | on HN ]