How to convert this prototype function into es6?

Question

// Converts snake-case to camelCase
String.prototype.toCamel = function () {
  return this.replace(/(\-[a-z])/g, $1 => $1.toUpperCase().replace('-', ''));
};

When I do the following:

// Converts snake-case to camelCase
String.prototype.toCamel = () => this.replace(/(\-[a-z])/g, $1 => $1.toUpperCase().replace('-', ''));

I get this error:

modifiers.js:9 Uncaught TypeError: Cannot read property 'replace' of undefined

How I'm using that toCamel function:

// Add style to coin
export const setStyle = (id) => {
  switch (id) {
    case 'basic-attention-token': return style.basicattentiontoken;
    case 'bitcoin-cash': return style[id.toCamel()];
    case 'deepbrain-chain': return style[id.toCamel()];
    case '0x': return style.zrx;
    default: return style[id];
  }
};

Possible duplicate of [Arrow function vs function declaration / expressions: Are they equivalent / exchangeable?](https://stackoverflow.com/questions/34361379/arrow-function-vs-function-declaration-expressions-are-they-equivalent-exch) — Scott, May 23 '18 at 01:06
The question's title is misleading. In your example you don't convert anything to ES6. You replace a regular function with an arrow function, which doesn't make any sense in this case. — a better oliver, May 23 '18 at 10:14

score 4 · Accepted Answer · answered May 22 '18 at 21:28

4

Arrow functions have lexical binding, so you can't use this in the way that you want to. In the case you have this is undefined and you can't read property 'replace' of it.

answered May 22 '18 at 21:28

Brett East

4,022
2
20
31

So there is no way to accomplish this then? It has to stay with `function`? – Leon Gaban May 24 '18 at 18:51
@LeonGaban that's correct, currently you would have to continue using `function` – Brett East May 30 '18 at 14:03

score 0 · Answer 2 · answered May 22 '18 at 21:31

0

The issue is that you are using an Arrow function.

An arrow function expression is lexically binding the this value. So, the value is bound to undefined. You have to use the normal function.

answered May 22 '18 at 21:31

user3619911

107
1
9

How to convert this prototype function into es6?

2 Answers2