Why does console.log behave like this?

问题

On the node.js interpreter:-

console.log("A newline character is written like \"\\ n \".");
//output is:-
// A newline character is written like "\ n ".

But when you simply enter this in the node.js interpreter:-

"A newline character is written like \"\\ n \"."
// it prints out:-
//'A newline character is written like "\\ n ".'

Does anybody now why this happened? Just curious to know more about node.js Thanks in advance for your answer.

回答1:

When logging a string, it gets fully parsed and every character gets escaped, and that's ok, it is the expected behavior.

Nonethless, displaying a string (not logging), the interpreter tries to show it in the simplest possible form. This will also avoid any misunderstanding for the user who's looking at it. So, basically:

Displaying "\"hi\"" will show '"hi"', because you can write a double quote inside a single quote delimited string without escaping it, and it's much easier to read.
Displaying '\'hi\'' will show "'hi'", for the same reason.
Displaying "\"hi\", 'hey'", with both single and double quotes, will force the interpreter to show you the original string (in the same form you created it), because there's no way to display it wothout escaping either the single or the double quotes, so it can only be shown as "\"hi\", 'hey'".

Try it by yourself:

var a = "\"hi\", 'hey'";
> "\"hi\", 'hey'"

var b = "\"hi\"";
> '"hi"'

console.log(a + ", " + b);
> "hi", 'hey', "hi"

来源：https://stackoverflow.com/questions/29191951/why-does-console-log-behave-like-this

标签

javascript

node.js

console.log