从变量中的字符串转义 JavaScript 中的双引号

Question

I have these two scenarios:

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console.log(('hello "friend" what\'s up?').replace(/\"/g, '\\"'));

I receive the expected result:

hello "friend" what's up?

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But , if I do this:

var val = 'hello "friend" what\'s up?';
val.replace(/\"/g, '\\"');
console.log(val);

I get...

hello "friend" what's up?

(the result needs to be hello \\"friend\\" what's up? )

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The only difference is that the second one uses an already created variable that contains the string. Why doesn't the second scenario actually replace the double quotes with \\" ?

Answer 1

From the MDN documentation :

The replace() method returns a new string with some or all matches of a pattern replaced by a replacement.

You need to do val = val.replace(/\\"/g, '\\\\"'); so that you're assigning the new string returned by calling replace to your variable.

Answer 2

Actually by doing

val.replace(/\"/g, '\\"');

You're not assigning the replaced value back to val . For that you will need:

val = val.replace(/\"/g, '\\"');

Answer 3

val.replace(/\"/g, '\\"');

In the above code you are not reassigning to val ;

Try this to get the expected result.

val = val.replace(/\"/g, '\\"');