Console log adding spaces between each character

Question

I wanted to have a console log of each socket message being sent down to the server, so I quickly wrapped socket.io's socket.emit function

    var self = this;
    this.socket = io.connect();

    this.socket._emit = this.socket.emit;
    this.socket.emit = function(){
        console.log(...arguments[0]);
        self.socket._emit(...arguments);
    };

It works fine except for some bizarre console log printing. This happens on Chrome and Firefox. What is going on?

I did fix this by using arguments[0] instead of ...arguments[0] but I'm still curious..

My guess was incorrect. I didn't know about the spread syntax. Full answer coming. — Phrogz
– Phrogz, Commented May 6, 2017 at 22:23

Phrogz · Accepted Answer · 2017-05-06 22:34:51Z

3

The spread syntax when used as the argument to a function call breaks the single string value into separate arguments for each character. The example below should make it clear.

var str = "abc";
console.log(str);         // abc
console.log(...str);      // a b c
console.log("a","b","c"); // a b c

var ary = [...str];
console.log(ary);         // (3) ["a", "b", "c"]

showArgs(...str);
function showArgs(x, y, z){
  console.log(x); // a
  console.log(y); // b
  console.log(z); // c
}

Why were you using console.log(...arguments[0])? What did you hope/expect to happen by using the ... there?

edited May 6, 2017 at 22:34

answered May 6, 2017 at 22:28

Phrogz

304k115 gold badges669 silver badges758 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

jozenbasin Over a year ago

I used ... to pass to the original function's implementation, and used it to print the arguments without thinking about it. It's still surprising because hovering over the ... object shows the string as a string.

Collectives™ on Stack Overflow

Console log adding spaces between each character

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related