Unescape an escaped string in JavaScript

Question

I'm running a loop to display characters of a specific Unicode escape sequence.

var es = '';

for (var i = 0; i <= 9999; i++) {
  if (i < 10) {
    es = '\\u000' + i;
  } else if (i < 100) {
    es = '\\u00' + i;
  } else {
    es = '\\u' + i;
  }
  console.log(es);
}

...however, it doesn't display the characters, just the sequence. Is there anyway in JavaScript to unescape the escaped sequence to force it show the character?

Answer 1

To do this, you'll want to use String.fromCharCode()

var es = '';
for (var i = 0; i < 9999; ++i) {
  es = String.fromCharCode(i);
  // ...
}

The \\uNNNN syntax only works with constant values inside the larger string constant.

edit — an important comment below points out that due to the problematic UTF-16 implementation of JavaScript strings, .fromCharCode() has problems with characters outside the Basic Multilingual Plane. For that, the ES6 (ES2015) has String.fromCodePoint() , a similar function that does handle "astral" characters outside the 16-bit range. More on that here and in the link in the comment.

Answer 2

For anyone stumbling across this question (most likely my future self) looking to "unescape" a previously escaped Javascript special characters , here's a hacky way to do it:

newString = JSON.stringify(string).slice(1,-1)

However this seems to only work for certain characters, like \\t , \\n , \\r , \\f , \\b , \\\\ , etc.

To explain myself better, in the case of tabs, this will convert a tab character back into literal/raw string that is \\t .

Answer 3

我遇到了来自 REST 端点的 JSON 响应的类似问题，这解决了它：

JSON.parse('"' + string + '"')