JavaScript转义字符串在Firefox开发人员工具上不起作用

Question

While I was trying the escaping strings on Firefox, I noticed that escaping strings don't work on Firefox Developer Tools , unless they are inside a console.log() or alert() message.

For example, if you just type inside the console the following message:

"The man whispered, \"please speak to me.\""

the result will be exactly the same with what you typed:

"The man whispered, \"please speak to me.\""

However, if you include the message in console.log() , then it works fine:

Input:

console.log("The man whispered, \"please speak to me.\"");

Output:

The man whispered, "please speak to me."

I don't know if it's some kind of bug or there's something deeper I'm not aware of, so I post it here and I hope someone could elaborate on that.

Answer 1

Firefox's Web Console is pulling double duty as a REPL environment and as the place where window.console dumps its output. When you type '"' in the Web Console, it reads and evaluates that string as a line of Javascript, and gives you the return value in a form it thinks you can use. Since '"' evaluates to a string, Firefox gives you that result as a string literal, "\\"" . But it still only contains one character, U+0022 QUOTATION MARK. You can see this for yourself with further testing:

» var str = '"'
⬅ undefined
» str
⬅ "\""
» str.length
⬅ 1
» str.charCodeAt(0)
⬅ 34

When you use console.log() , on the other hand, the Web Console is dumping the objects given to console.log as log messages. Firefox has a different idea of what makes a useful log message: for strings, an easy-to-read message is better than a string literal you could copy back into your code. Thus,

» console.log(str)
  "                                     debugger eval code:1:1
⬅ undefined

Note the undefined at the bottom: the Console is still REPLing. The " line is console.log intruding on your conversation.