Regex for string starting with quote but not with escape character

Question

I have to find a string which start and end with double quotes and then change its color. But if there is escape character (/) with quote then it will not be considered as string and color will not be changed.

For example:

1. "hello"
2. \\"hello\\"

The first example will be considered as string while the second example will not be considered as a string.

How to write a regex in javascript which only returns a string which starts and ends with double quotes but there should not have any escape character (/)

Answer 1

Don't need a regex here - simple first character check with charAt :

 const strings = [`"hello"`, `\\\\"hello\\\\"`]; strings.forEach(s => console.log(s.charAt(0) == `"`));

If you really need a regex:

 const strings = [`"hello"`, `\\\\"hello\\\\"`]; const regex = /^[\\"]/; strings.forEach(s => console.log(regex.test(s)));

Answer 2

A possible solution would be using JSON.parse() , since a string like "hello" is also a valid JSON object, while a string like "hello\\" is not.

function checkString(str){
    try {
        // let's try to parse the string as a JSON object
        const parsed = JSON.parse(str);
        // check if the result is a valid javascript string
        return (parsed === String(parsed));
    }
    catch(error){
        return false;
    }
}

EDIT:

If you have an array of objects, and you need to find which object is a valid string, you can do this:

const strings = ['"valid string"', '"not valid string\\"'];
const validStrings = strings.filter((e) => {
    return (e === String(e) && checkString(e));
});

Answer 3

You can use this pattern

^(?!.*\/)".*"$

• ^ - start of string
• (?!.*\\\\) - condition to avoid any \\
• " - Matches "
• .* - Matches anything except new line
• $ - End of string

 const strings = [`"hello"`, `\\\\"hello\\\\"`, `\\\\"hello`, `hello"\\\\`, `"hel/lo"`,]; strings.forEach(s => { if(/^(?!.*\\\\)".*"$/.test(s)){ console.log(s) } });