javascript - How to create a polyfill for spread operator - Stack Overflow

I was trying to create a polyfill for the spread operator. My objective is to create something similar to spread operator where instead of triple dots I can use triple @@@ symbols.

For example, in ES6

function sum(x, y, z) {
  return x + y + z;
}

const numbers = [1, 2, 3];

console.log(sum(...numbers));
// expected output: 6

I was trying to implement similar functionalities

// Instead of triple dots, it should be triple @
console.log(sum(@@@numbers));
// expected output should be 6

I expect the output of console.log(sum(@@@numbers)); to be 6.

I was trying to create a polyfill for the spread operator. My objective is to create something similar to spread operator where instead of triple dots I can use triple @@@ symbols.

For example, in ES6

function sum(x, y, z) {
  return x + y + z;
}

const numbers = [1, 2, 3];

console.log(sum(...numbers));
// expected output: 6

I was trying to implement similar functionalities

// Instead of triple dots, it should be triple @
console.log(sum(@@@numbers));
// expected output should be 6

I expect the output of console.log(sum(@@@numbers)); to be 6.

• javascript
• ecmascript-6
• polyfills

Share Improve this question Follow asked Jul 18, 2019 at 10:10 Saswata ArabindaSaswata Arabinda 56722 gold badges88 silver badges1717 bronze badges 7

• 11 It's impossible, because what you're doing violates Javascript syntax, and syntax is not polyfillable. Transpileable, sure, but not polyfillable. – CertainPerformance Commented Jul 18, 2019 at 10:11
• so any workaround ?? – Saswata Arabinda Commented Jul 18, 2019 at 10:19
• No - like I said, it's impossible – CertainPerformance Commented Jul 18, 2019 at 10:19
• You can of course just write sum.apply(null, numbers), but you cannot introduce your own syntax. – Bergi Commented Jul 18, 2019 at 10:26
• 1 @SaswatArabinda There is no way to define custom syntax in JavaScript. You need to use a transpiler that piles your custom syntax to working code - and of course then you should just use a usual transpiler that piles the real spread syntax into legacy code. – Bergi Commented Jul 18, 2019 at 10:31

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1 Answer 1

Sorted by: Reset to default 9

You cannot create a polyfill for spread operator.

The proper way to deal with such backward patibility issues is to write your code in ES6, and use transpiler like babel to convert it to ES5 automatically.